TBMN occurs in at least 1% of the population and has been known benign disease. But in recent reports, some doctors presented that TBMN had progressive course. We experience Alport syndrome in 19-year old male patient who was diagnosed as TBMN 6 years ago. At that time, urine analysis revealed proteinuria (2155 mg/day) with 10~29RBCs/HPF. After diagnosis, he lost of follow up. During loss of follow up period, he had progressive nephritis with prominent proteinuria(2402 mg/day), declining renal function(BUN 30.1 mg/dL, creatinine 2.7 mg/dL, glomerular filtration rate of 18.2mL/min by Tc99m DTPA renal scan), sensorineural hearing loss and recurrent corneal erosion. We performed repeat renal biopsy and the result of second biopsy was consistent with Alport syndrome. He was managed conservatively with ARB(Telmisartan) and prednisolone. After 3 month, TP/Cr ratio of spot urine decline from 3549 mg/dL to 478 mg/dL and creatinine level mild improved to 2.2 mg/dL. In conclusion, we recommend clinicians should exercise caution and observe the course of disease when patients had prominent proteinuria, familial history and other extra-renal manifestations, even if TBMD.