In the present article some theoretical and practical issues will be offered about the relationship between the professional translator and scientific discourse. To answer the question on how the professional translator translates or ought to translate scientific discourse the concept of translation will be delimited and the theoretical principles founded on discourse analysis and the functionalist approach to translation will be reviewed. Based on a corpus of different types of texts (specialized, semispecialized and journalistic) some of the main characteristics of scientific discourse at the interlinguistic, intercultural, and pragmatic levels will be presented in order to clarify what is expected of the professional translator that faces this type of discourse.)