OBJECTIVE To determine whether adolescents with varicoceles experience physiologic testicular "catch-up" growth during development, thereby providing a role for conservative management of adolescent varicoceles. METHODS An internal review board-approved retrospective chart review of the Children's Hospital of Eastern Ontario patient database was conducted. Patients presenting with a varicocele between January 1999 and January 2005 were selected. Varicocele grade, ultrasound-determined testicular volume differential over time, and need for surgery were recorded. The difference between left and right testicular volume at diagnosis and at study completion was compared and statistically analyzed. RESULTS A total of 33 boys with a median age of 13.4 years (range, 8.8 to 16.1 years) was selected. Patients presented with clinical varicocele grades 3 (63.6%), 2 (33.3%), and 1 (3.0%). Of 33 patients, 3 (9.1%) required surgery for pain (1) and increasing testicular size discrepancy (2). A significant decrease was observed in the percentage difference between left and right testicular volumes over time (P = 0.017). This remained significant even after adjustment for age, length of observation, and need for surgery (P = 0.026). Of 14 patients with an initially significant difference in testicular volume (greater than 20%) who were managed conservatively, 7 experienced testicular catch-up growth (volume differential less than 20%) (P = 0.016). CONCLUSIONS Some adolescent boys with a varicocele and considerable testicular size discrepancy manifest significant testicular "catch-up" growth during continued physiologic development. However, those patients who show a testicular size discrepancy that is steadily increasing should be considered for surgical intervention.