The efficiency of testicular sperm retrieval by testicular fine needle aspiration (TEFNA) was compared with open biopsy and testicular sperm extraction (TESE), in 37 rigorously selected patients with non-obstructive azoospermia. All patients underwent TEFNA and TESE consecutively. Thus, each patient served as his own control. The case was regarded as successful if at least one testicular spermatozoon was found allowing intracytoplasmic sperm injection (ICSI) of at least one oocyte. The mean age of the male patients was 32.7 years (range 24-47). Whereas by TEFNA spermatozoa enabling performance of ICSI were found in only four patients out of 37 (11%), open biopsy and TESE yielded spermatozoa in 16 cases (43%). The negative predictive value of high serum follicle stimulating hormone (FSH) concentrations (> or =10 IU/l) (predicting failure to find spermatozoa for ICSI) was low (38.4%). The positive predictive value (predicting the chance to find spermatozoa for ICSI) of normal-sized testicle was not different from that of small-sized (<15 ml) testicle (50%). Complications included one case of testicular bleeding following fine needle aspiration, treated locally, and two cases of extratunical haematomata following TESE requiring no intervention. In patients with non-obstructive azoospermia, TEFNA has a significantly lower yield compared to TESE. Performance of ICSI with testicular sperm in these cases resulted in satisfactory fertilization and high embryo transfer rates. The implantation and pregnancy rates per embryo transfer were 13 and 29% respectively. Neither serum FSH values nor testicular size were predictive of the chances to find spermatozoa for ICSI. Some complications may occur even following TEFNA.