Fibrinolytic activity and tissue plasminogen activator (t-PA) level were measured in 33 healthy individuals prior to and after fibrinolytic system stimulation (i.e. a ten-minute venous stasis). Fibrinolytic activity was measured with the aid of euglobin lysis time, and lysis test on the fibrin plates (in own modification). Tissue plasminogen activator concentration was assayed spectrophotometrically with the COA-SET t-PA (Kabi Vitrum). No fibrinolytic activity of plasma specimens taken before the venous stasis was noted during fibrin lysis plate test whereas it was seen in 13 subjects after the venous stasis. Fibrinolytic activity of the plasma euglobins, measured as a surface on fibrin plates, increased significantly after the venous stasis in both sexes (by 35.5 mm2 on the average, i.e. by 51%). It was more marked in men than in women both prior to and after venous stasis (by 10.9% and 19.0%, respectively). A time of plasma euglobin lysis was shorter after venous stasis (by 110 minutes, on the average). There was no significant difference between the sexes. Tissue plasminogen activator concentration increased by 5.8 times (from 1.7 IU/ml to 9.9 IU/ml) after the stasis. Correlation between t-PA concentrations and fibrinolytic activity, measured on the fibrin plates, was highly positive. No such a correlation existed between t-PA concentrations and the time of euglobin lysis. The obtained results indicate variety of assessments of fibrinolytic system activity.(ABSTRACT TRUNCATED AT 250 WORDS)