The workshop of the brothers Agnolo and Donnino del Mazziere has only recently emerged as having been a significant artistic enterprise in Florence during the late fifteenth and early sixteenth centuries. In 1988 the brothers' work, previously known only through descriptions in archival documents, was convincingly linked to a body of paintings and drawings ascribed to an anonymous artist called the "Master of Santo Spirito."
The elder brother, Donnino, achieved little notice in his time. He appears only in the tax documents of his father, Domenico di Donnino Mazziere, and in the records of the payments he received as the apparent head of the brothers' workshop. This independent enterprise began sometime after 1480, when Donnino was recorded as working without salary (probably as an apprentice) in an unnamed artist's studio. Through his younger sibling's greater prominence, however, we can surmise that the training ground for both artists was the studio of the traditionalist painter Cosimo Rosselli.
Agnolo di Domenico del Mazziere is mentioned by Vasari in the life of Rosselli and given a brief biography by Filippo Baldinucci. According to the former, Agnolo was a skilled draftsman and remained a close friend of Cosimo Rosselli's until the master's death in 1507. Since he was better known in artistic circles than Donnino, he presumably was more talented. That he was recognized as a painter of some technical proficiency is further attested by the fact that Michelangelo included him among the artists called to Rome in 1507-1508 to consult on preparations for the Sistine Chapel ceiling. Vasari also possessed several drawings he attributed to Agnolo and included some of them in his Libro de' Disegni. Among these were portraits of Cosimo Rosselli and the young Benedetto da Rovezzano, which Vasari subsequently used as models for the two men's woodcut images in his Vite. Only Baldinucci, in his later biographical note, gives a hint of Agnolo's stylistic development, saying that he eliminated "a certain dryness of the contours" in his later works.
The Mazziere brothers seem to have established their own shop by the late 1480s. A series of documented payments from 1490 through 1515 attests to their activity in Florence and elsewhere in Tuscany, where they produced altarpieces and fresco decorations for churches, confraternities, and the Florentine government. Although some documents mention both brothers, the majority address payment to Donnino, presumably the managing partner. Although existing records do not distinguish between the brothers' artistic contributions for any given commission, scholars assume that the bottega was a collaborative enterprise. It seems to have remained rather fluid, employing other artists on occasion for individual projects, while permitting Agnolo in 1508-1509 to work on a fresco program commissioned to another master in the Rosselli orbit--Cosimo's cousin, Bernardo di Stefano Rosselli. Such flexibility in studio practice appears to have been rather common in late fifteenth-century Florence. Following Agnolo's death in 1513, the shop continued its activity at least until Donnino is last mentioned in 1515.
The earliest recorded painting of the Mazziere studio, an altarpiece of 1490 for the hospital church of Santa Lucia in Florence (formerly located near the portal of San Frediano), appears to be the brothers' only documented altar panel to survive. Astutely traced by Anna Padoa Rizzo to the Enthroned Madonna and Child between Two Angels and Saints Lucy and Peter Martyr in the Gallerie dell'Accademia, Venice, it had previously been attributed to the Master of Santo Spirito. The picture is thus the crucial piece of evidence linking the recorded creations of the Mazziere brothers with the corpus of paintings ascribed to the Master of Santo Spirito.
Federico Zeri devised this name in 1962 for the painter of a small number of stylistically similar works, including three altarpieces from the late 1480s and 1490s in the Augustinian church of Santo Spirito in Florence. These core paintings, and the other works later attributed to him in steadily increasing numbers, reveal an artistic sensibility of a determined traditionalist nature, steeped in the stylistic approaches worked out in Florence during the 1470s and 1480s.
The authorship of a single artist or workshop for the substantial body of works given to the Master of Santo Spirito has received general scholarly acceptance. Although there have been other proposals, Padoa Rizzo's well-reasoned identification of this oeuvre with the workshop of Agnolo and Donnino del Mazziere benefits from the agreement between records of the brothers' activity and the traditionalism and presumed dating of the paintings; it has likewise received support. Scholars do not, however, have the same confidence in distinguishing Agnolo's and Donnino's individual hands. The documents are vague, and it is too arbitrary to presume that the more sophisticated features are by the more talented Agnolo, while the more archaic aspects belong to the older Donnino. Although the drawings attributed to Agnolo have many features in common with heads in the existing paintings, our knowledge is still too limited to recognize a given painting as anything more precise than a product of the brothers' workshop.
In analyzing the oeuvre, Federico Zeri detected strong traces of Cosimo Rosselli and a significant current from Lorenzo di Credi; others have noticed stylistic features and specific motifs from Domenico Ghirlandaio, Filippino Lippi, Jacopo del Sellaio, Pietro Perugino, Bernardo Pinturicchio, and (in the landscapes and portraits) such northern masters as Hans Memling. The Mazziere brothers, whose responsibility for the Master of Santo Spirito's work seems plausible, melded the more advanced elements of various contemporary artists' works in their own. [This is the artist's biography published, or to be published, in the NGA Systematic Catalogue]
 The earlier bibliography and documents for the Mazziere brothers have been brought together by Padoa Rizzo 1988, 125-132. See also Bacci 1906, 1-12; Colnaghi 1928, 180; and Anna Forlani, "Agnolo di Domenico di Donnino," in DBI, 1 (1960): 449.
 For the suggestion that Agnolo was a student of Cosimo Rosselli, see Colnaghi 1928, 180, and Anna Forlani, "Agnolo di Domenico di Donnino," in DBI, 1 (1960): 449. Padoa Rizzo 1988, 128, first suggested that both Agnolo and Donnino were disciples of Rosselli.
 Vasari, ed. Milanesi, 3 (1878): 190-191; Baldinucci (1681), Ranalli ed., 1 (1845): 542-543; and Padoa Rizzo 1988, 125-126.
 Vasari, ed. Milanesi, 3 (1878): 190. Vasari describes Agnolo's relation to Cosimo Rosselli as "suo amicissimo."
 Vasari, ed. Milanesi, 3 (1878): 191.
 Ragghianti Collobi 1974, 1: 73, and 2: figs. 198, 199; Parker 1929, 58-60.
 See Padoa Rizzo 1988, 128-131, figs. 1, 2, for the woodcuts.
 Baldinucci (1681), Ranelli ed., 1 (1845): 543: "non lascia di scoprire una certa secchezza ne' dintorni, la quale non si vedde poi nell'altre pittore sue."
 Payments are recorded specifically to Donnino, however, for his 1499 frescoes on the corbels of the dome of the former church of Santa Chiara in Pistoia. See Bacci 1906, 8. Bacci discovered the painted figures under whitewash, and they have subsequently been recovered; see Padoa Rizzo 1988, 147, figs. 14-17. They are the only frescoes by either brother known to have survived.
 For the hiring of other artists, see Vasari, ed. Milanesi, 3 (1878): 191 note; and Bacci 1906, 3. For Agnolo's work with Bernardo Rosselli in 1508-1509, see Padoa Rizzo 1988, 127-128. In 1504 Donnino painted a tondo for the Camera del Gonfaloniere in the Palazzo Vecchio with one Domenico di Pietro Aghinetti, who is described as "suo compagno"; perhaps this overlapped with Agnolo's work in the same year for a series of monochrome frescoes for the confraternity of Gesù Pellegrino (see Vasari, ed. Milanesi, 3 : 191).
 See Exh. cat. Florence, Maestri e botteghe 1992 for the often complex relations of master painters, students, and collaborators in later fifteenth-century Florentine shop practice.
 For the altarpiece and its connection with the Mazziere brothers, see Padoa Rizzo 1991, 54-63, repro., and Exh. cat. Florence, Maestri e botteghe 1992, 122-123, no. 3.8.
 Padoa Rizzo 1991; Cecilia Filippini in Exh. cat. Florence, Maestri e botteghe 1992, 122, fig. 3.8.
 Zeri 1962, 218, 236 note 2. Fahy (1968) 1976, 192-195, considerably expanded the list of works attributed to this artist. See also Dalli Regoli, Madonna, 1984, 213-232. Richard Offner apparently named the Master of Santo Spirito and gave him a group of works earlier and independently of Zeri (see Zeri 1976, 1: 109).
 Horne 1905, 189-196, proposed Giovanni di Michele da Larciano (Il Graffione), as the author of a number of works from this oeuvre, an identification Fahy until recently supported (see Fahy  1976, 192).
 Padoa Rizzo 1988 and 1991; Exh. cat. Florence, Chiesa e città 1992, 181, no. 8.10; Goguel 1992, 125. Fahy reported his agreement with Padoa Rizzo's identification in a letter of 11 February 1993 (in NGA curatorial files).
 Goguel 1992, 125, stresses the need for caution in distinguishing between each brother's contributions.
 Zeri 1962, 236 note 2, and 1976, 108. Capretti 1991, 43, cites Lippi, Ghirlandaio, Sellaio, and the Flemish. Goguel 1992, 124, also cites influences from the North, including Dürer.