The authors have eased the burden of data collection by employing information systems designed to accept data in familiar formats, guide users through protocols, and enforce the recording of important items. Such strategies are used in two large, independent studies of patients with myocardial infarctions: a natural-history and an acute drug-intervention study. MUMPS information systems, in conjunction with a data manager, serve as essential ingredients of the data collection processes. As tasks are completed, data are entered, edited, and then manipulated to define future paths in the protocol. Later data are passed to a SAS database for statistical analysis.