This article briefly investigates the role that ethno-methodology has played in sociological analyses of language and interaction. The work of Harvey Sacks is investigated in relation to membership categorization and the analysis of talk-in-interaction. More specifically, the authors focus on how this strand of work has been developed in recent years and now represents a powerful apparatus for conducting sociological analyses of interaction in a diverse range of settings in a way that is sensitive to issues related to social organization, normativity, identity, macro-micro synthesis, knowledge and developments in social theory. © 2002, Sage Publications. All rights reserved.