This paper presents a review of recent research that examines the relative instructional utility of text-based synchronous and asynchronous computer-mediated communication (CMC). As a mechanism for limiting the number of studies reviewed as well as controlling for emergent technologies, only research published since 2000 was reviewed. The goal was to synthesize empirical evidence regarding the instructional effectiveness of synchronous and asynchronous online discussion. Comprehensive search of academic databases and online journals identified research that compared: (1) students using asynchronous-postings with students in face-to-face discussion; (2) students using synchronous-chat with students in face-to-face discussion; and (3) students using both asynchronous-postings and synchronous-chat. Within each of these three comparison groups, a variety of criterion is used including objective and subjective measures of student achievement, student satisfaction and perceived value of learning experiences, evidence of higher-level thinking skills, and amount, type and substance of communicative exchange. (Contains 1 figure.)