Benign prostatic hyperplasia is common in aging men, but rare in childhood. We report a case of juvenile prostatic hyperplasia in a 10-year-old boy, who visited our clinic for hematuria and voiding symptoms. Radiologic studies revealed a huge prostate protruding into the bladder. The prostate was 33 g. The prostate biopsy showed no evidence of cancer. At 13 years of age, he was seen again because of general weakness, fever, and voiding difficulty. Bilateral hydroureteronephrosis was found on radiologic studies, and his serum creatinine was elevated. The prostate was 55 g. Suprapubic prostatectomy was performed.