Prior studies have investigated sperm retrieval rates in men with nonobstructive azoospermia (NOA) secondary to specific etiologies,yet most cases of NOA are idiopathic.We compared sperm retrieval rates and testicular histopathology in idiopathic NOA (iNOA) and nonidiopathic NOA (niNOA).We performed a retrospective review of men with NOA who underwent microdissection testicular sperm extraction (microTESE) between 2000 and 2016.Men with no history of malignancy or cryptorchidism and negative genetic evaluation were considered idiopathic.Multivariable regression determined the association between idiopathic etiology and primary outcomes of sperm retrieval and active spermatogenesis on histopathology.Among 224 men,86 (38.4％) were idiopathic,75 (33.5％) were nonidiopathic,and 63 (28.1％) did not undergo genetic testing.Median age and serum testosterone were higher among iNOA or no testing versus niNOA.Median follicle-stimulating hormone (FSH) was lower among iNOA or no testing versus niNOA.A higher proportion of iNOA or no testing versus niNOA had a clinical varicocele.Sperm retrieval rates were similar between iNOA,niNOA,and no testing (41.8％ vs 48.0％ vs 55.6％,respectively;P =0.255).Active spermatogenesis was seen in a higher proportion of iNOA or no testing versus niNOA (31.4％ and 27.0％ vs 16.0％,P =0.073).On multivariable analysis,iNOA was not associated with sperm retrieval or spermatogenesis (P =0.430 and P =0.078,respectively).Rates of sperm retrieval and spermatogenesis on testis pathology were similar in men with iNOA and niNOA.These data will be useful to clinicians in preoperative counseling for men with NOA and negative genetic evaluation.