This study explores the effects of the use of Second Life (SL) as a learning environment on a course's dialogue. An experimental design within groups was used with thirty-seven graduate students for three weeks. Half of them followed the course activities in the official Learning Management System (LMS) of the program, Blackboard Vista, and the other half in the 3D Virtual World (VW), SL. Results revealed significant differences in the copresence of the two groups, which can be explained by sensory and availability factors of the media used. The study also detected qualitative differences in students' collaboration in the two environments and in their satisfaction with interaction. The findings support the use of 3D Virtual Learning Environments (3DVEs) for instruction and teamwork in distance education in a blended mode setting. (Contains 5 tables.)