A current set of concerns in ethnomethodology and conversation analysis includes the question of how conversation analysis (CA) can deal with studies of social structure or studies of talk in institutional settings.In this paper a focus is placed on how the accomplishment of "work" and "categorization" are interrelated. Two particular instances are examined: a ski school and a package delivery service. Membership categorization is shown to be a complex, on-going, interactive accomplishment. The parties act in ways that are "predicatively-bound" (i.e. (...) predicates of action, rights, obligations, etc.) which allow inferences to be made by each of the parties about the other based on these actions; these enable each to accept/confirm/validate the other's self-categorization and to produce, via their own actions, activities that are congruent with the other's self-categorization. Activities of the parties are category-relevant and category-generative. Thus, "work" or "the work of the organization", (e.g. for Choice, a package delivery service), is being accomplished in and through the talk and interaction of the parties. (shrink)