A project of group-based peer review by general practitioners is described. Attention is given to the motivation of general practitioners to participate in audits, to the threat posed by peer review and to the use of criteria. The recruitment and motivation were successful. A total of 253 general practitioners took part, divided into 23 groups. This represented approximately 30% of all general practitioners in the area and 72% of all general practitioners specifically approached by us. The threat posed by audit disappears rapidly for most physicians once they have started auditing. The use of predefined criteria developed by 'experts', representing an optimal way of work for the general practitioner, appeared to be quite feasible in this project. From the results several conclusions are drawn as regards the planning and implementation of peer review under general practitioners.