In most clinical trials it is problematic to recruit enough patients within a reasonable time period. Prolonged or inefficient recruitment or both can have negative scientific and economic consequences. The XENDOS (XENical in the prevention of Diabetes in Obese Subjects) study is an ongoing randomized, double-blind, placebo-controlled, prospective, multicenter trial investigating whether orlistat combined with hypocaloric diet and moderate physical exercise can reduce the incidence of diabetes in obese subjects. To implement the XENDOS protocol and recruit the study patients, we designed a system for centralized patient recruitment and centralized scheduling of patients and staff at the 22 collaborating centers. The recruitment and inclusion phase was divided into a series of different consecutive examinations of increasing complexity. Relatively simple initial examinations enabling a large throughput of patients were followed by more detailed examinations of fewer subjects, by then known to fulfil some of the study-specific requirements. With the aid of object-oriented techniques, the software was modularized to enable concurrent engineering. We also selected a structure where plug-in modules handling specific tasks could be added to the system as needed. The design was supported by a flow-oriented view of the progress of the patients through the study. With this overall solution we managed to include 3305 subjects (98.8% of the requested number) within less than 4 months. The sex distribution (44.8% men) and the number of patients with impaired glucose tolerance (IGT), (21.1%) were in close accordance with, or far better than, the requirements of the protocol (45% men, at least 10% IGT patients). The basic design of the XENDOS information system can be adapted to fulfil the requirements of other study protocols within the fields of obesity, diabetes, hypertension, coronary heart disease, etc. Shortening the recruitment and inclusion phase of large clinical trials is of great value both to be medical society and the pharmaceutical industry.