OBJECTIVES Two cases of 46,XX true hermaphroditism were analyzed for two Y-DNA sequences, including the recently cloned gene for male testis determination, the sex-determining region of the Y chromosome (SRY). METHODS Polymerase chain reaction was performed to amplify the SRY. DNA was prepared from peripheral blood lymphocytes as well as from gonadal tissue preserved in a paraffin block. RESULTS One hermaphrodite contained the SRY sequences in peripheral blood lymphocytes and the testicular part of ovotestis tissue preserved in a paraffin block, while in the second patient these sequences were not detected. CONCLUSIONS The SRY positive subject resulted from occult Y mosaicism rather than from X-Y translocation. Testis differentiation in the SRY negative subject may have been caused by mutation of a gene on the X chromosome or, alternatively, on an autosome.