The classification of azoospermia into obstructive or non-obstructive is largely based on medical history, physical examination and biochemical markers in serum and semen. However, the most accurate parameter for diagnosis is the testicular histology. The predictive value of the percutaneous epididymal sperm aspiration (PESA), FSH, LH, testosterone, inhibin-B and testicular volume was investigated for their accuracy to predict a complete spermatogenesis (Johnsen score > or =8) in order to replace the testicular histology. The specificity and sensitivity of FSH, inhibin-B, LH, testosterone, testicular volume, and the presence of sperm in a PESA procedure was evaluated in 147 azoospermic males attending the centre for infertility diagnosis. A positive PESA outcome presented the highest sensitivity and specificity to predict a Johnsen score > or =8 (93 and 94% respectively) compared with FSH (90 and 19%), inhibin-B (88 and 57%) and testicular volume (95 and 45%). Differences in clinical presentation were observed between patients with positive sperm retrieval with PESA, depending on the aetiology of obstruction. In conclusion, the presence of spermatozoa in the epididymis (PESA+) correlates with a Johnsen score > or =8 and is the most accurate parameter to predict complete spermatogenesis compared with clinical or biochemical parameters. Between obstructive azoospermic patients, the clinical parameters observed varied according to the aetiology.