Nineteen patients with hereditary nephritis - members of six families - were studied for haemostasis on 11 occasions by the use of four capillary tests, 14 different blood coagulation tests and two different platelet function tests. Systemic capillaropathy was demonstrable in 8 out of 15 cases of the non-uraemic, and in all the 5 cases of the uraemic group. No completely normal blood coagulation was found in any of the cases and the coagulation disorders were never of exclusively haemorrhagic pattern. On the evidence of the complex studies, hypercoagulability as well as hyper-hypocoagulability were found in the uraemic and non-uraemic groups alike. Reduction in plasma fibrinolytic activity, elevation of the fibrinogen level and a shift of the thrombelastogram in the direction of thrombosis were demonstrable in the majority of the cases.