Membership Categorisation Analysis (MCA) developed as a refocusing of Harvey Sacks’ original analyses of categories, devices, and sequence in talk-in-interaction. In building empirically an understanding of membership categorisation practices as ‘culture-in-action’, MCA, and this collection, opens up an attention to categorisation practices, in all their forms, as means of doing ethnomethodology and sociology. Indeed, MCA has become a prominent methodological and analytic approach across the social sciences and a range of topics of study as a powerful form of ethnomethodologically grounded inquiry. The aim of this collection is to showcase the cutting edge of MCA research and future new directions.