This seminar will examine the possibilities and constraints of online communities in supporting teacher learning, both novice and experienced teachers, so addressing the national concerns for teacher retention and teacher quality in the USA. In particular, the speaker will focus on outlining a conceptual and methodological framework for characterizing interaction of experienced and novice teachers in informal network-based professional learning electronic or e-communities. The study has shown that integrating dialogic voices/utterances (Bakhtin, 1986) and using texts as ���thinking device[s]��� for generating new meanings (Lotman, 1990; Wertsch, 1991) are essential for effectively engaging practitioners. Using both qualitative and quantitative methods, longitudinal discourse data, questionnaires, and interview responses were collected from public school teachers��� email communications and subjected to analyses from discourse analytic and ethnographic perspectives, resulting in a characterization of engagement and a taxonomy of e-communities for evaluations. The findings suggest proposals for sustainable learning in network-based environments and policy.