This paper discusses different reasons which may incite both NS and NNS speakers to depart from the present tense convention in scientific English, using data from a reception study in which 45 readers from eight countries evaluated and annotated the same three discussion sections written by Dutch biologists. The influence of NNSs' competence in English, mother tongue interference and non-anglophone tense conventions for reporting past events were examined. The readers' responses to the preponderance of present tense in the texts appeared to be inconsistent. Possible explanations are suggested and the implications of the results for writers, teachers, editors and reviewers are discussed.