Our focus in this article is on some uses of categorial transformations. The discussion is divided into two main parts. In the first part, we begin by outlining our approach, namely membership categorization analysis (MCA), indicating the origins of the term and elaborating the conception of MCA as an "occasioned' members' apparatus. We then explain what we mean by the concept of categorial transformation, review some of the very few previous studies which have investigated this phenomenon and which are pertinent to its further study, and indicate how categorial transformation serves to embody and illustrate the occasionality of MCA. In the second part of the article, we present an analysis of two extracts from a transcript of the naturally occurring talk-in-interaction which occurred in a particular family meal, involving two children and their parents. A variety of categorial transformation practices in this data are identified and their particular local usages described. In the concluding discussion we consider our argument and our analysis in light of previous discussions of the trajectory of Sacks' work.