The purpose of this paper is to begin to try to understand the extent to which ethnomethodology (EM) might be informed by some concepts and ideas from the work of the philosopher Martin Heidegger. This is done in two parts. The first looks at Heidegger's later work and compares his conception of the ontological difference with Garfinkel's work on the difference between EM and formal sociological analysis (FA). The second part turns to Heidegger's earlier work (around Being and Time) and works through a number of affinities between the analysis of Dasein and ethnomethodological versions of everydayness.