The coagulation profile of 25 patients with brain tumours was studied preoperatively, intraoperatively and postoperatively. Ten patients had abnormal coagulation status preoperatively. Surgical intervention led to either an alteration of preexisting abnormality or appearance of new coagulation abnormality. Disseminated intravascular coagulation and fibrinolysis occurred with equal frequency in patients with meningiomas and gliomas. The alterations as a result of surgery were transient and compensated rapidly.