This article reports on the generic characteristics of thesis abstracts by the Persian, English and speakers of other languages in seven disciplines. To this aim, 552 abstracts were selected and analyzed in terms of macro- and micro-structures. Findings revealed obligatory structures by the researchers regardless of their language background. However, findings also showed optional structures. Cultural and disciplinary differences appeared to affect the selection of the latter structures. In the second phase of the study, the authors provided explicit instruction to a group of Persian researchers on the macro- and micro-structures. Results showed that explicit knowledge of rhetorical structures can greatly enhance the quality of English abstracts. Further studies are required in order to account for disciplinary variation and the native language influence on the production of academic texts in English.