Two unrelated girls presenting with developmental delay were found to have familial Y-autosome translocations. The first had a Y;15 and the second a Y;22 translocation, involving only the Y heterochromatin on the basis of Q, C, SS, distamycin A and DAPI techniques. The first patient died of a medulloblastoma and at autopsy was found to have an adrenal neuroganglioma. The Y-autosome translocations in the affected patients were identical to those in their respective normal fathers (who had normal Y chromosomes as well). The absence of detectable translocated euchromatin from the subcentromeric region of the Y chromosome is consistent with normal female external genitalia and the absence of germ cell tumors in both patients. Whether the nongonadal neoplasias and hypoplastic uterus and ovaries in the first patient were related to the Y;15 translocation remains uncertain.