As in many other Passions written to be set to music, the figure of St. Peter is of extraordinary importance in Metastasio's oratorio. A feature that drew the attention of both librettists and composers was the subject of "Peter's Lament"; taken as a moving expression of deeply-felt penitence, this theme was also the subject matter of the long-established literary tradition of "The Tears of St. Peter", which had throughout figured in Baroque piety and also proved popular in the figurative arts. This article discusses the dramatic role and the significance of the theme in three different settings of Metastasio's "Passion" (Caldara, 1730; Jommelli, 1749; Paisiello, 1782) and also in the Viennese world in which Metastasio's work would be introduced. For this second question, a number of other works treating the theme considered at Guadagni and Pietro Andrea Ziani's "Oratorio di San Pietro piangente", Pariati and Fux's "Gesù Cristo negato da Pietro" and Francesco Sbarra's "Il lutto dell'universo" (with music by the emperor Leopold I). Certain theological and biblical features of the gospel story are analysed in explanation of the continuing popularity of the theme in seventeenth/eighteenth-century Europe.