Objectives. To evaluate the incidence of left and right varicocele in adolescents. Methods. The study group consisted of 28 adolescents who underwent evaluation for varicocele at our clinic. In 19 patients, varicocele was detected on routine physical examination, and 9 patients presented with scrotal pain or discomfort. All patients were evaluated by three methods. Physical examination was followed in all cases by contact thermography and venography studies of both testes. Results. The rate of left and right retrograde flow in the spermatic veins by the three methods used was as follows: physical examination 92.8% and 10.7%; contact thermography 100% and 89%; and venography 100% and 85.7%, respectively. Varicocele was not detected by physical examination in 2 (7.2%) of the 28 patients on the left side and in 21 (87.5%) of 24 on the right side. Conclusions. The main finding of this study was that varicocele is a bilateral disease in 85.7% of adolescents. The high percentage of bilateral varicocele in our sample may explain the pathophysiologic mechanism whereby what has traditionally been considered a unilateral disease can produce bilateral testicular dysfunction. The high incidence of subclinical bilateral varicocele may indicate that we should consider varicocele a bilateral disease. The second finding was that only 10% of patients with right varicocele were diagnosed by physical examination and more than 85% were diagnosed by thermography, with confirmation by venography. Therefore, we suggest that thermography and venography should play a major role in the diagnosis of varicocele.