To investigate the efficiency of microdissection TESE (Micro-TESE) for sperm recovery in patients with nonobstructive azoospermia (NOA). A retrospective study. Between June 2002 and December 2006, 970 azoospermic men who were diagnosed as NOA underwent micro-TESE operation for ICSI treatment. All men evaluated with physical examination, serum FSH and total testosterone levels and semen analysis. Peripheric karyotype analysis showed nonmosaic Klinefelter's syndrome (KS) in 95 patients. Y microdeletion analysis showed AZFc deletion in 10 patients. Ninety-six men had a history of orchiopexy operation and nine men had a history of mumps orchitis. Micro-TESE operation was performed on the day of oocyte pick up by the same surgeon. Spermatozoa were successfully retrieved in 512 of 970 (52.8%) TESE procedures. Mean age of the men, serum hormone levels and testicular volume did not show any difference between successful and failed recovery attempts. The success rates of sperm recovery as correlated to their etiological patterns are 48.5% in men with nonmosaic KS, 67.7% in men with orchidopexy operation, 50% in AZFc microdeletion and 77% in men with a history of mumps orchitis. The success of sperm recovery was significantly higher (63%) in men with KS who were younger than 35 years of age as compare to men older age (25%). Micro-TESE is successful technique in azoospermic men with atrophic testis due to KS, mumps orchitis or cryptorchidism. The younger age of men with KS has higher rate of successful sperm recovery with micro-TESE.