The papers collected in this special issue examine specific instances of autism research, treatment and advocacy. Their shared aim is to explore not the causes, but the manifold biosocial consequences and theoretical implications of the recent expansion of the autism spectrum. Three such implications are singled out in the introduction as common threads running through all the papers. First, the extent to which developments in the field of autism research, treatment and advocacy pose a challenge to theories of ‘biomedicalization’ and ‘geneticization’. Second, the intimate connection between autism’s recalcitrance to be pinned down and explained and its enormous biosocial productivity. Third, the need to broaden Hacking’s (1998, 2006) concept of ‘looping’ to make sense of the ‘moving target’ that is autism.