Scrotal temperatures, testicular volumes, and sperm characteristics were studied in 150 infertile, nonazoospermic men and in 37 fertile men, used as a control group. The mean scrotal temperature values of the infertile men were significantly greater than those observed in the fertile men (+0.4 degrees C for the right; +0.5 degrees C for the left). In the infertile men, it was found that the higher the scrotal temperature, the more alterated the sperm characteristics. The only clinical element that seemed to be linked to the existence of scrotal hyperthermia in the infertile men was testicular hypotrophy. Although the scrotal temperatures of the infertile men with varicocele were significantly higher than those of the fertile men, they did not significantly differ from those of the infertile men without varicocele. No other specific pathologic factor, infectious or surgical urogenital history was found to be responsible for the scrotal hyperthermia observed in the infertile men.