In an attempt to characterise further the coagulopathy of childhood nephrotic syndrome, this study concentrates on simultaneous measurements of the natural anticoagulants [antithrombin III (ATIII), proteins C and S] and the fibrinolytic factors, tissue plasminogen activator (tPA) and plasminogen activator inhibitor (PAI). The study groups consisted of 41 children (ages ranging from 2 to 14 years; median 7.1) in the relapse of nephrosis and 48 children (ages ranging from 3 to 14 years; median 7.6) in remission. The results obtained were compared with normal values obtained in healthy age- and sex-matched controls (n = 103). During relapse, there was a marked increase in the plasma level of fibrinogen, protein C, and protein S and reduced plasma ATIII level; tPA level was similar to control but PAI level exhibited a significant reduction. During remission, the protein C level either remained elevated or increased further, but some decreased. Protein S and plasma ATIII level normalised. The fibrinolytic activator tPA dropped slightly but the PAI level remained significantly below control levels. We conclude that in the relapse of childhood nephrosis, despite the existence of a significant prothrombotic tendency as featured by hyperfibrinogenaemia and markedly reduced ATIII level, the simultaneous elevation of the natural anticoagulant, protein C level and enhanced fibrinolysis that persist until the remission phase, seem to be major preventive mechanisms guarding nephrotic children against thromboembolic phenomena.