The ethnographic analysis of categories is still largely based on assumptions of cultural uniformity, although, during the past decade, the significance of variation has become increasingly evident as attempts have been made to measure it. Delineation and measurement are themselves complex tasks, however. In a single body of data there may be variation according to many criteria which are often cross-cutting and reinforce each other irregularly. These issues are discussed in this paper in relation to different types and contexts of variation evident in animal classifications of the Nuaulu of eastern Indonesia. Yet, the kinds of assumptions made in formal studies of individual variation are as problematic as those concerning cultural uniformity. It is important to appreciate that the techniques and representations employed to describe classifications and their variation are often inadequate, concealing those things that are operationally of most significance and reifying ‘classifications’ which do not always exist in practice. The products of classifying behaviour inevitably reflect the immediate social conditions of the situations in which they are used. (Analysis of categories, cultural variability, ethnozoology, social context; Nuaulu of eastern Indonesia.)