The importance of measuring healthcare performance and outcome rapidly grows around the world. As hospital information systems (HIS) become more commonplace, their use as clinical research tools can be easily developed. This is demonstrated in the article by two examples of clinical outcomes research undertaken on the world's largest HIS database. The research studies described in the article were on: (1) The effect of hospital 'experience' on inpatient mortality rates for patients with HIV-related pneumocystis carinii pneumonia, and (2) The effect of streptokinase and tPA on post-acute myocardial infarction survival rates.