As some studies shown a decrease of successful sperm retrieval with the increasing of age, we plan to compare the potential of sperm retrieval between two groups "adult" (23-55 years) and "young" after the onset of puberty (15-22 years). The study will be performed by searching spermatozoa on two seminal analyses spaced out 3 months followed by a testicular biopsy if the azoospermia is confirmed on semen analyses.