['To determine the effect of a palpable left-sided varicocele (which in adolescent patients can adversely affect left testicular volume) on right testicular volume with progressive Tanner development and increasing varicocele grade.', 'The right and left testicular volumes were measured with a standard orchidometer in 70 control patients (mean age 14.6 years, SD 2.2) with no palpable testicular abnormality and in 434 (mean age 14.3 years, SD 2.3) with a palpable left-sided varicocele. Patients with bilateral and right-sided varicoceles were excluded from the study.', 'There was no significant difference between the left and right testicular volumes in the control patients. The testicular volumes of patients with a grade I varicocele were similar to those in control patients. Patients with a grade II varicocele had a significantly smaller left testis than the controls at Tanner stages 4 and 5 (P < or = 0.05). Patients with a grade III varicocele had a significantly smaller left testis than controls at each Tanner stage (P < or = 0.05) and significantly smaller right testis than controls at Tanner stages 4 and 5 (P < or = 0.05).'] Does varicocele in adolescence induce left and right testicular volume loss?