A newborn with ambiguous genitalia appeared to have male pseudohermaphroditism caused by partial insensitivity to androgens associated with a subnormal level of androgen receptors in cultured genital skin fibroblasts. This hitherto infrequently diagnosed condition has genetical and prognostic implications regarding fertility. The causes of male pseudohermaphroditism and the repercussions of partial androgen insensitivity are discussed.