Regimento proueytoso contra ha pestenença and Modus curandi cum balsamo are probably the first texts addressing the prevention and treatment of diseases to be printed in Portugal. Their authorship and historical context are discussed elsewhere in this journal. Here we would like to raise some questions concerning the 'medical discourse' found in the texts and compare these with others from the eighteenth century. The authors chosen for the sake of comparison are two Portuguese--Luiz Gomes Ferreyra and João Curvo Semmedo--and one Englishman, John Huxham, author of An Essay on Fevers, which includes a lengthy discussion of smallpox, Europe's eighteenth-century 'plague'. It is our belief that these works, written in the early days of 'scientific medicine', represent a bridge between medieval/Renaissance texts and current medical compendia. They allow us to raise questions about the therapeutic indications and diagnostic criteria found in the documents.