Introduction: Discontent and litigation among patients is a problem which increasingly preoccupies the medical profession. Aim: We aim to analyse the origin of discontent and litigation and to help avoiding these claims. Material: One hundred and seventy-eight medical expert opinions were evaluated, all made following examination of the complainant. Methods: Depending on the results of the clinical examination and the study of the files it was determined whether there was either a case of malpractice or insufficient informed consent, or no fault at all in a legal sense. In addition the patient and the surgeon were questioned as to their point of view regarding the procedure and their communication and relationship before and after treatment. Results: Frequent complaints were pain (either during treatment or afterwards), major swelling or bleeding, disturbances of trigeminal or facial nerve function, poor scar formation, loss of teeth or fixtures, faulty occlusion and discrepancies between the expected and the actual result of treatment. In 26 cases actual faults made during medical treatment were discovered. In 49 further cases, poor explanation of the proposed procedure was the reason for complaint. In the majority of remaining cases, neither faulty treatment nor insufficient information given to the patient lead to the complaint but the patient's expectations were unrealistically high. Conclusion: A considerable proportion of lawsuits originate from misunderstandings, and not treatment errors: The surgeons often concentrate on the legal requirements of informed consent and neglect to explain the practical consequences of the operation; the patients in turn tend not to ask about possible complications. Copyright 2001 European Association for Cranio-Maxillofacial Surgery.