This paper is a description of the first collaborative research project of a self-initiated teacher development group in South India. All five members who undertook this research are practising teachers who, at one time or another in their professional lives, have taught ESL classes of over a hundred students at pre-university or undergraduate level. This paper illustrates their use of talk to make sense of their collective teaching experience by focusing on the central issue of heterogeneity. The paper spells out the dialogic process initiated and sustained by the group over eight months, during which the members developed their initial anecdotal accounts into a complex understanding of their pedagogic hypotheses and principles. The cognitive and social value of the group's interaction, the insights from its research, and the modes of facilitative talk and writing it evolved might be useful to teacher-researchers in other contexts. © 1992 Oxford University Press.