OBJECTIVE: To report repeated successful induction of fertility in an adult male patient with congenital adrenal hyperplasia (CAH) and testicular adrenal rest tumors (TART). DESIGN: Case report. SETTING: Radboud University Nijmegen Medical Centre. PATIENT(S): A 23-year-old male CAH patient with bilateral TART and azoospermia. INTERVENTION(S): Changing glucocorticoid medication from 30 mg of hydrocortisone to 0.75 mg of dexamethasone (DXM) daily. MAIN OUTCOME MEASURE(S): Improved semen analysis. RESULT(S): With the use of ultrasound screening, TART were detected in the 23-year-old patient. The semen analysis showed azoospermia. In an attempt to decrease tumor size and improve testicular function, his glucocorticoid medication was changed from hydrocortisone to an equivalent dosage of DXM. The azoospermia was quickly reversed, and his partner conceived within 7 months of stopping oral contraceptives. Due to his progressive weight gain and striae, his medication was changed back to hydrocortisone, and he again developed again azoospermia. Two years later, the patient started again with DXM at the same dosage. His sperm concentration increased with progressive weight gain. Seven months later his partner became pregnant for the second time; afterward, the DXM treatment was changed back to hydrocortisone. CONCLUSION(S): In male CAH patients with testicular adrenal rest tumors, infertility may be reversible by replacing hydrocortisone with short courses of an equivalent dosage of DXM.