Asynchronous computer mediated learning (CML) provides a mechanism for student interaction that is unique among educational delivery systems. Collaborative interactive learning can lead to deeper learning than is possible without interaction among learners and may enable groups of learners to become more knowledgeable than the teacher in narrow areas. This paper outlines principles and strategies for promoting student interaction and collaboration in CML settings. Assumptions of constructivist learning are outlined that related to cultural context, social constructivism, social needs, development of constructions (schema) in CML, authentic learning, scaffolding in the zone of proximal development, and teaching methods. Collaboration is defined, along with aspects of collaborative learning: communities of practice, functional skills, peer exchanges, and reciprocal teaching. Strategies to develop interaction include coaching (a subset of scaffolding), collaboration under teacher control, and consideration of alternative CML materials. Learner motivation in CML is addressed. Interactive teaching strategies are discussed, including use of artifacts, complex material, and scaffolding; peer teaching strategies; cognitive apprenticeships; and intergenerational communities of learners (links between earlier and later groups of learners). (SV)