A 12-year-old boy with a left-sided varicocele (Grade 3) was assessed preoperatively and followed postoperatively by computer-assisted infrared thermography. The temperature of the left scrotum was 35.4 degrees C before surgery which was 4 degrees C higher than that of the right scrotum. After ligation of the left internal spermatic vein and removal of the varicocele, scrotal thermograms 39 days and 12 months after operation were normal. Therefore, it seems that thermography is very valuable in the evaluation of testicular function in children with varicocele, in whom semen analysis is impossible.