The combined occurrence of hereditary nephritis with nerve deafness (Alport's syndrome) and macrothrombocytopathic thrombocytopenia is very rare. The authors have had the opportunity to study such a case in a 20-year-old man who had been followed since birth. The clinical history, renal biopsy, platelet studies, and autopsy findings are presented. The renal pathologic findings are well defined; however, the hemostatic abnormalities and the hearing loss are not well characterized. In this paper, an attept is made to clarify the diverse platelet functional and morphologic abnormalties.