A balanced reciprocal translocation t(Y;1)(q12;q21) was found in an azoospermic male. Using the testicular sperm extraction (TESE) and intracytoplasmic sperm injection (ICSI), the patient had a boy who was found to have the same translocation. They were revealed to have a balanced reciprocal translocation by G-, C-, R- and high resolution banding. Fluorescence in situ hybridiation (FISH) with the probe chromosome Yq heterochromatin and C-banding were confirmed that the breakpoint is in Yq12 heterochromatic region. It was known that deletion of the AZF region of the Y chromosome is most frequent molecularly defined cause of spermatogenic failure. Especially the DAZ (deleted in azoospermia) gene is expressed exclusively in the human male germ line, and is frequently microdeleted in azoospermic men. To detect the small deletion in AZF gene, we studied on seven loci (sY84, 129, 134, 156, 254, 255, 269) including 3 DAZ regions. Also three loci (SRY, DYZ3. DYZ1) on the short arm, centromere and long arm respectively were amplified. Microdeletion of 10 loci was not detected in infertile male and his son. The results indicate that the infertility of this patient could be due to alteration of the sequence order of Y chromosme or to a disturbance of X chromosome inactivation as a result of the proximity to the autosomal portion.