Computer-mediated distance education holds potential for providing professional development opportunities for teachers. This study investigated teaching and learning through written asynchronous and synchronous communications in an online graduate education course. Types of student participation during four weeks of discussions in the course, two weeks involving discussion boards (asynchronous) and two involving chat sessions (synchronous), were analyzed to better understand the instruction and learning taking place through each mode. Surveys of students' perceptions of various aspects of the online course including their learning through discussion boards and chat sessions were gathered. Findings suggest instructional practices for online education that draw on the strengths of each written communication mode while diminishing their weaknesses. (Contains 1 figure.)