Deletion of DAZ gene copies is related to spermatogenesis impairment. To investigate the distribution of DAZ gene copy deletions among Chinese men, we analyzed DAZ gene deletions by multiplex polymerase chain reaction (multi-PCR) and polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) in 128 infertile patients with severe oligozoospermia selected as semen donors for intracytoplasmic sperm injection (ICSI) and 287 normospermic men. Three patterns of DAZ gene deletions, namely DAZ1/DAZ2 deletion, DAZ3/DAZ4 deletion and complete deletion of all 4 DAZ copies, were found in the present study. Complete deletion of the entire DAZ family of genes was only present in 11.7% of severe oligozoospermic patients. The frequency of DAZ1/DAZ2 deletion was significantly higher in severe oligozoospermic patients than that in the controls(9.4% vs 2.8%, P = 0.004. The total frequency of complete DAZ deletion and DAZ1/DAZ2 deletion was 21.1%. No significant difference in the frequency of DAZ3/DAZ4 deletion was observed between the patient and control group (7.0% vs 3.8%, P > 0.05). These results suggest that complete DAZ deletion is a frequent genetic cause of severe oligozoospermia, and DAZ1/DAZ2 deletion is a high risk factor for the disease. Thus, it is necessary to screen the two deletion patterns of DAZ genes in severely oligozoospermic sperm donors before ICSI during assisted reproduction.