Task discretion has held a central place in theories of work organization and the employment relationship. However, there have been sharply differing views about both the factors that determine it and the principal trends over time. Using evidence from three national surveys, this article shows that there has been a decline in task discretion since the early 1990s. This contrasts with an increase in other forms of employee involvement such as direct participation and consultative involvement. Many of the arguments in the literature about the factors that favour higher task discretion are supported by our evidence — in particular those emphasizing the importance of skill levels and the broader organizational ethos with respect to employee involvement. However, such factors do not account for the decline in task discretion, implying that existing theories fail to address some of the crucial determinants. It is tentatively suggested that it may be necessary also to take account of macro factors such as competitive pressure, public sector reform programmes and the growth of accountability structures.