Summary Studies of platelet function in four kindreds affected with the Bernard‐Soulier Syndrome are summarized. Platelet aggregation induced by ADP and by dilute collagen suspensions was normal, but the increase in optical density and platelet “volume” that normally proceeds aggregation was lacking. Platelet aggregation by bovine fibrinogen was totally deficient, and the rate of aggregation by both ADP and collagen was abnormally rapid. The serum prothrombin time was abnormal, but other tests of platelet factor 3 activity were normal, as were estimates of platelet adhesiveness. The lack of initial platelet “swelling” and deficient bovine fibrinogen‐induced platelet aggregation are heretofore unrecognized features of this disorder that may provide information as to the nature of the underlying abnormality.

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A family with combined deficiency of factor VIII and factor IX is reported. Family study showed that the father and his nephew had mild factor VIII deficiency with normal von Willebrand factor antigen and factor IX levels while his two sons had a reduced level of factor IX and normal factor VIII levels. His wife was found to have marginally reduced factor IX levels, whereas his daughter had reduced or normal levels of both factors VIII and IX. DNA analysis using the intra- and extragenic markers of factor VIII and IX genes showed that mother is a carrier of haemophilia B and the daughter is a carrier for both haemophilia A and B. Thus, the combined deficiency observed was due to a chance association of two distinct genetic defects.