We studied the fibrinolytic response before and after venous occlusion (VO) in 30 patients with systemic lupus erythematosus (SLE), 25 with rheumatoid arthritis (RA) and 25 with different connective tissue disorders. Results were compared in patients with and without antiphospholipid antibodies (APA) and a history of either thrombosis or abortions. Before occlusion plasma levels of tissue-type plasminogen activator (t-PA) antigen and its inhibitor (PAI-1) were significantly higher in the patient group (p < 0.001). After occlusion, a low fibrinolytic activity on fibrin plates (p < 0.005) was observed in the same group. t-PA capacity and t-PA release were similar in relation to controls. The plasma PAI-1 activity was significantly elevated in each group of patients (p < 0.005) as compared to the control group. No significant differences with respect to t-PA and PAI-1 were observed in patients as to the presence or absence of thrombosis. There was also no correlation between the fibrinolytic changes and the presence of APA. It is concluded that an impairment of the fibrinolytic system, mainly related to increased PAI-1 levels, is present in most patients with connective tissue disorders, although these changes did not correlate with the presence of APA or the incidence of thrombosis.