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.

This report summarizes information obtained on four generations of a kindred afflicted with a mild hemorrhagic diathesis. Studies carried out on a family of eight members and platelet counts obtained on fifty-one additional members demonstrated only mild thrombocytopenia in eleven members of three generations. The thrombocytopenia appears to be inherited as an autosomal dominant trait.

The case of an 11-year-old girl with a severe bleeding diathesis, a factor IX level of 4 per cent, and 45, X Turner’s syndrome is described. Family studies revealed severe factor IX deficiency in 4 male relatives and mild deficiencies in 4 heterozygous female carriers. The Bm or B+ variant of this disorder was demonstrated in all affected members of the kindred.