Open AccessThis paper studies evidentiality in a corpus of medical research papers in English and Spanish. We concentrate on sentential evidentials, i.e. evidentials affecting a complete proposition, in both languages. We will show that these devices are more frequent in English than in Spanish, although the two languages use similar constructions to show authors’ source/mode of information. Our study considers evidentials found in the different research sections in order to detect and describe intrageneric differences. This research aims to contribute (1) to the characterisation of the medical research papers in both languages, and (2) to the debate concerning the relationship between evidentiality and epistemic modality. Our view is that they represent two distinct categories. The interpretation of evidentials in terms of authorial commitment is a pragmatic effect perceived by readers/hearers. This approach leads the analyses of the examples to conclude that the two concepts are autonomous, although readers may infer other pragmatic values.