Twenty two patients (12 males and 10 females) from all over Israel fulfilled the criteria for establishing the diagnosis of Glanzmann's thrombasthenia. All have been observed to have a servere bleeding tendency since infancy or early childhood. In 8 out of 10 adult patients (7 females and 3 males) the bleeding manifestations have persisted over the years. In 2 adult patients major surgery was performed under platelet transfusions which appeared to prevent excessive bleeding. Pedigree analysis was possible for 21 patients who belong to 13 unrelated kindreds. Twelve kindreds are Jewish and one is Arab. Eleven of the 12 Jewish kindreds belong to the Iraqi Jewish community. Analysis of 16 sibships disclosed a corrected segregation ratio of 0.2, which is compatible with an autosomal recessive mode of inheritance. No bleeding manifestation whatsoever were observed in 30 obligatory carriers of thrombasthania, and the haemostatic functions tested in 12 of them were entirely normal.