To evaluate the first year's experience of an informal patient complaints system that encourages extensive patient participation. Audit of an informal complaints procedure. The Marylebone Health Centre, London. 39 complaints received over the audit period. Types of complaints (administrative, about doctors or medical care or both, staff about patients, mixed, other) and resolution of complaints (how complaints were dealt with and their resolution). 37 of the 39 complaints were resolved within two weeks. Two complaints sent direct to the family health services authority were resolved (with patients' agreement) by the informal complaints procedure. The informal complaints procedure was more cost effective than the family health services authority system and was comparatively straightforward to implement within the practice without major organisational restructuring. The two way process of the procedure ensured patients received a quick response to complaints and helped morale of health centre staff.