The azoospermia factor (AZF) region is important for spermatogenesis,and deletions within these regions are a common cause of oligozoospermia and azoospermia.Although several studies have reported this cause,the present research,to the best of our knowledge,is the first large-scale study assessing this factor in Japan.In this study,1030 male patients with infertility who were examined for Y chromosome microdeletion using the polymerase chain reaction-reverse sequence-specific oligonucleotide (PCR-rSSO) method,a newly developed method for Y chromosome microdeletion screening,were included.The study enrolled 250 patients with severe oligospermia and 717 patients with azoospermia.Among the 1030 patients,4,4,10,and 52 had AZFa,AZFb,AZFb+c,and AZFc deletions,respectively.The sperm recovery rate (SRR) of microdissection testicular sperm extraction in patients with AZFc deletions was significantly higher than that in those without AZF deletions (60.0％ vs 28.7％,P =0.04).In patients with gr/gr deletion,SRR was 18.7％,which was lower than that in those without gr/gr deletion,but was not statistically significant.In conclusion,our study showed that the frequency of Y chromosome microdeletion in male patients in Japan was similar to that reported in patients from other countries,and SRR was higher in patients with AZFc deletion.