The article examines the disciplinary preferences of medical and psychology writers of research articles (RAs) in the use of epistemic lexical verbs (ELVs), regarding their frequency, prominence, distribution across the RA sections, and recurrent phraseology. The results show that disciplinary affiliation affects these phenomena, as more ELVs are found in psychology than in medicine. Both groups prefer speculative judgements and quotative evidence and most frequently use ELVs in Discussions. Yet, psychology authors are more balanced in their preferences and rely on a wider selection of frequent ELVs which are often combined with self-mention. Medical authors are more inclined towards deductive ELVs. Disciplinary differences are also observed in the choice of the specific ELVs, their frequency distributions and phraseology in the distinct RA sections.