The incidence of varicocele in adolescent males has been reported to range from 6% to 19%. Our objective was to evaluate if there was any correlation between either varicocele grade or testicular volume and gonadotropin responses to gonadotropin-releasing hormone (LHRH) in 55 adolescents with grade (G) 2 and 3 varicocele, mean age 14.0 years (range: 10-16.8), Tanner stage I, n: 2; II, n: 9; III, n: 15; IV, n: 22; V, n:7. Testicular volume was assessed with Prader orchidometer. Basal and post LHRH serum gonadotropins were determined by radioimmunoassay. Varicocele grades were 2, n: 9; 3, n: 40; bilateral, n: 6. In patients with Tanner stage IV-V, there was a significant correlation between varicocele grade and LH area under the curve post LHRH, r: 0.45. Ipsilateral testicular growth arrest was present in 33 patients (60%) and mean left testicular volume was 77.4 +/- 9.6% (mean +/- SD) when compared to right testicular volume. LH response to LHRH was higher (p < 0.05) in those patients with left testicular volume less than 80%. In conclusion, the finding of higher LH response to LHRH in our patients with more severe ipsilateral testicular growth arrest suggests early Leydig cell dysfunction; both factors can be potential predictors of surgical indication.