This presentation explores the categories of evidentiality, i.e. the mode of knowing, and epistemic modality, i.e. judgements about certainty, in a corpus of English and Spanish abstracts in the field of medicine written in the last decades by native speakers of these languages. Our notion of abstracts follows the description of the genre provided Bondi and Lorés-Sanz (2014). The analyses of epistemic modality and evidentiality are based on the works of Plungian (2001), Marín-Arrese (2009), and Cornillie (2009), Alonso-Almeida (2015a), among others, and these allow us to establish a differentiation between evidential and epistemic legitimating strategies. For this, lexical and grammatica units will be considered in our analysis of research article abstracts. In doing this, we seek to explore and describe the functions of evidential and epistemic devices in the scientific domain in two different languages. This study has, therefore, two main objectives: (a) to identify and categorize evidential and epistemic markers in our corpus of English and Spanish medical abstracts, (b) to describe the functions these strategies fulfil in the abstracts, and (b) to see whether these strategies are register-dependent, i.e. whether there are differences according to the language used. In the light of earlier evidence on research articles from a contrastive perspective (AlonsoAlmeida 2015b; Almeida & Pastor 2017), we expect abstract to show more cases of epistemic modality in the case of the English texts, as English texts have been shown to rely on this type of modality in order to convey politeness within the community of scientists for which these abstracts are aimed at (Carrió-Pastor & Calderón 2015).