Most governments in established market economies have developed universal systems of health care, but these are being increasingly threatened by widespread health sector reforms. Hence, it is more important than ever to monitor the effects of policy changes on the ability of universal systems to achieve their equity goals. This article provides evidence for such monitoring. The authors present the results of a systematic review of equity in use of curative health services in universal systems, together with a critical appraisal of the essential components of studies to address this question. Of the 79 studies identified that addressed the review question, only 26 met the inclusion criteria and adjusted for differential health need across socioeconomic groups. The authors found a pro-rich bias in use of specialist hospital services and a reasonably equitable access to primary health care by different socioeconomic groups. There was a wide inter-study variation in the difference in utilization rates between people of high and low socioeconomic groups. Improvements are needed in the way that equity in universal systems is monitored, with particular attention to how "need" is defined and to the impact on patients of indirect costs.