To identify patients who had Ullrich-Turner syndrome (UTS) and were at risk for gonadoblastoma or associated germ cell tumors, molecular genetic analysis was carried out to detect Y chromosomal sequences. From peripheral blood samples of 5 patients who had cytogenetically confirmed UTS, genomic DNA was extracted and screened for Y chromosomal sequences by polymerase chain reaction. The morphology of the gonadal tissues was compared with results from polymerase chain reaction. Three phenotypic females showed UTS mosaicism with normal X chromosome accompanied by Y chromosomal material, and 2 patients showed marker chromosomes. Molecular analysis represented loci PABY, SRY, ZFY, TSPY, DYZ3, DYZ1 DXYS, 19Y, DYS-273, DYS-148, DYS218, DYS224, and DYZ1. Three patients showed gonadal tumors (1 with unilateral gonadoblastoma, 1 with unilateral dysgerminoma, and 1 patient had both tumors in 1 gonad). Molecular genetic screening for Y chromosomal sequences may be useful as an additional tool for the identification of patients at risk for a gonadal tumor. Careful, complete processing, including step sectioning, of the gonadectomy specimens to detect small lesions is recommended.