Any chromosomal abnormalities associated with otosclerosis would be most likely to appear among persons exhibiting familial otosclerosis. Blood from 13 otosclerotics representing three families was analyzed by short-term culture of peripheral blood leukocytes. The four men exhibited normal male karyotype (46,XY) and the nine women normal female karyotype (46,XX). The findings do not confirm the contention by Tato et al1 that otosclerotics are characterized by peculiarity of chromosomal number and morphology.