How ethnomethodology and conversation analysis (CA) relate to one another is often poorly understood. This is especially the case when CA is picked up by other disciplines, often drawing heavily from the 1974 publication on conversational turn-taking in the journal Language by Sacks, Schegloff, and Jefferson, and overlooking how Harvey Sacks initially “invented” and developed CA as an ethnomethodological approach to sequential analysis. This chapter draws upon Sacks’ published lectures, unpublished manuscripts, and notebooks to draw out the extent to which he developed sequential analysis as reflective of ethnomethodology's abiding concern with the formal structures of practical actions as described in Chapter 1. Sacks focused on the methods members use to organise conversation as a practical and concerted achievement. He contrasted this conception from conventional, constructive analytic approaches in sociology. This chapter provides a baseline for considering later developments in CA that diverged from Sacks’ ethnomethodological approach in favour of a rapprochement with constructive analysis.