After acquiring the strong colouring and other distinctive stylistic features of the Lombard school and – though he is not known to have travelled to Milan[3] – somehow absorbing the superficial mannerisms of Leonardo,[4] he travelled to Siena before 1503, perhaps at the behest of agents of the Spannocchi family, and began with fresco cycles for Olivetan monks and a series of small Ovidian ceiling panels and a frieze depicting the career of Julius Caesar for Sigismondo Chigi at Palazzo Chigi.

His first important works were frescoes in the Benedictine monastery of Monte Oliveto Maggiore, on the road from Siena to Rome, illustrating the life of St Benedict in continuation of the series that Luca Signorelli had begun in 1498.

[6] Gaining fluency in the prevailing popular style of Pinturicchio, Sodoma completed the set in 1502 and included a self-portrait with badgers and ravens.

[7] Sodoma was invited to Rome in 1508 by the celebrated Sienese merchant Agostino Chigi and was employed there by Pope Julius II in the Stanza della Segnatura in the Vatican.

He executed two great compositions and various ornaments and grotesques[6] in vaulted ceilings divided into feigned compartments in the antique manner that Pinturicchio had recently revived, working at the same time as Raphael.

Giorgio Vasari's rhetorical story that Sodoma's larger works did not satisfy the pope, who engaged Raphael to substitute a program of Justice, Poetry, and Theology, is not borne out by the documents.

According to Vasari's testimony, Bazzi always surrounded himself with "boys and beardless youths, whom he loved more than was decent", for which reason he acquired the nickname Il Soddoma.

In the Oratory of San Bernardino, are scenes from the history of the Virgin, painted in conjunction with Girolamo del Pacchia and Domenico di Pace Beccafumi (1536–1538).

[6] Vasari alleges that Sodoma was always a negligent artist, his early success in Siena, where he painted many portraits, being partly due to lack of competition, a judgment in which Sydney Freedberg concurs.