The Portuguese theory of thorough-bass between the eighteenth-century and the early nineteenth century reflects the musical moment experienced by Portugal in the Baroque era. Under strong Italian influence, the preponderance of musical practice in Portugal alternates between the repertoire of church music from Roman style, and the secular music, represented by operas, serenades and instrumental works. The musical styles found in this period reflect the coexistence of both secular and church music, which also characterizes the theory of thorough-bass. In this paper I try to analyze aspects of performance from five prominent Portuguese treatises, published between 1735 and 1806, in order to find evidence of contemporary musical practice.1225770