This study explored the benefits and drawbacks of synchronous voice-based computer-mediated communication (CMC) in a blended course of English for specific purposes. Quantitative and qualitative data from two groups following the same syllabus, except for the oral component, were compared. Oral tasks were carried out face-to-face with same L1 partners in the control group and through synchronous voice-based CMC with different L1 partners in the experimental group. The analysis included data from general proficiency pre- and post-test scores, oral Power Point presentation grades, students' questionnaires and students' and teachers' diaries. The results showed that achievements were significantly better in the experimental group and that there was also an increase of other positive factors which may effectively contribute both to second language acquisition (SLA) and to solving many of the problems which make speaking skills the weakest skill in foreign language contexts. (Contains 4 notes and 3 tables.)