This paper discusses the preliminary results of a systematic review of the literature on applied usability studies of health information systems in the period 1990 to 2006. Abstracts were included when they described an evaluation of the usability of a health information system. To gain insight into usability methods applied and their properties we constructed a framework to analyze the studies. The framework includes objectives, designs, number of participants, user-profiles, settings, medical domain, and type of health information systems evaluated. Fifty-two Papers were included in the review. Findings show that from 2002 an increasing trend can be observed of publication of usability studies. Most studies discuss summative usability results on working systems thereby focusing on systems' adoption problems. Formative usability studies lack a uniform way to describe how study results contributed to the system's iterative development cycle.