In patients with congenital adrenal hyperplasia, testicular adrenal hyperplasia and tumors can develop. A three-year-old boy was admitted to our hospital with complaints of enlarged penis and development of pubic hair. 11beta-hydroxylase deficient congenital adrenal hyperplasia was diagnosed and hydrocortisone treatment was started. His family did not accept treatment well and did not come for check-ups regularly, which is why his metabolic control was poor. In ultrasonographic evaluation, a hypoechoic mass, 10x10 mm in size, was detected in his left testis at 15 years of age and steroid dose was increased. Almost two years later the tumor completely disappeared with high dose steroid treatment. In conclusion, the monitoring of congenital adrenal hyperplasia with ultrasonography is recommended, especially in puberty, because it is important that testicular adrenal rest hyperplasia should be determined before testicular adrenal rest tumors develop. In this case we observed that small testicular adrenal rest tumors disappeared completely with high dose steroid treatment in nearly two years.