In 30 patients with objectively diagnosed and 13 with clinically diagnosed venous thrombosis during pregnancy the extension and localization of the thrombotic process was analysed in relation to the coagulation and fibrinolytic status at least 6 months after thrombosis. Left-sided thrombi pre-dominated, being more extensive and proximal on the left side. Most thrombi started during the last two trimesters. Few changes were found in the coagulation system. Nineteen per cent of the patients showed a defective fibrinolytic system, as diagnosed by a reduced release capacity and/or a reduced fibrinolytic activity in the vessel wall. No great differences were found between patients with clinical vs. objective diagnosis.