A body of literature on self-tracking has been established in human-computer interaction studies. Contributors to this literature tend to take a cognitive or behavioural psychology approach to theorising and explaining selftracking. Such an approach is limited to understanding individual behaviour. Yet self-tracking is a profoundly social practice, both in terms of the enculturated meanings with which it is invested and the social encounters and social institutions that are part of the selftracking phenomenon. In this paper I contend that sociological perspectives can contribute some intriguing possibilities for human-computer interaction research, particularly in developing an understanding of the wider social, cultural and political dimensions of what I refer to as 'self-tracking cultures'. The discussion focuses on the following topics: self-optimisation and governing the self; entanglements of bodies and technologies; the valorisation of data; data doubles; and social inequalities and self-tracking. The paper ends with outlining some directions for future research on self-tracking cultures that goes beyond the individual to the social.