The syndrome of hereditary thrombocytopenia, deafness, and renal disease was manifest in at least eight members in three generations of a family. They had a lifelong history of bleeding, usually as epistaxis, bilateral sensorineural deafness starting in late childhood or the teenage years, and persistent proteinuria with varying degrees of renal dysfunction. Two members died at a young age, one from central nervous system hemorrhage, the other from chronic renal failure. Splenectomy and steroid therapy have been of transient benefit. There was dominant inheritance of the syndrome. Hematologic studies showed thrombocytopenia, large platelets, and megakaryocytic hyperplasia of the bone marrow. In contrast to a previous report, our studies showed that affected members had normal in-vitro platelet function and normal ultrastructural platelet morphology. At autopsy, histologic changes in the kidney of one affected family member were indistinguishable from those reported in classic hereditary nephritis with nerve deafness (Alport's syndrome).