The Truth Maintenance Workshop was held in August 1990 during the European Conference on Artificial Intelligence in Stockholm, Sweden. Ten selected papers, eight of them presented at the workshop, are included in this volume. The papers can be grouped into four main areas: - Meta-level control: the goal here is to specify some meta-criteria to control the behavior of the TMS. - Extensions of TMS: here the aim is to incorporate new mechanisms into TMS-like systems. - Foundations: there is now much interest in providing formal descriptions of TMS, proving results about them, and relating them with other non-monotonic formalisms. - Belief revision: TMS can be considered as providing support to manage the more general problem of belief revision.