We report a 12-7/12 year-old male with obesity, eunuchoid proportions, genetic stigmata of Turner's syndrome and mild developmental delay. We investigated whether cytogenetic alterations could be responsible for his phenotype. Conventional karyotype in 70 peripheral blood cells was 45,X(15%)/46,XYqh-(85%). Dual FISH on 1,000 nuclei revealed 8% of X0 cells (DXZ1 X-centromeric probe) and 92% of XY cells (DYZ3 Y-centromeric probe). We studied Y chromosome microdeletions by PCR. The patient showed a terminal Yq deletion from the 5I interval including the AZFb and AZFc regions. FSH, LH and testosterone (468 ng/dl) were within the normal range for his age. At Tanner IV pubertal development the spermiogram showed azoospermia and the testicular aspirate spermatic arrest. The present report suggests that Y chromosome deletions including AZFb and AZFc regions may cause spermatogenic arrest in early puberty.