<p>Klinefelter' syndrome is a disorder of sexual differentiation in males, characterized by the presence of two or more X-chromosomes, hypogonadism, and lack of secondary sexual characteristics. The association between Klinefelter' syndrome and glomerulonephritis has been reported, while cases of glomerulonephritis associated with Klinefelter' syndrome are rare. We report the Korean case: a 31-year-old man with Klinefelter' syndrome who developed glomerulonephritis. The patient's urine analysis shows microscopic hematuria and the result of kidney biopsy was minimal change disease. The onset and course of his disease might have been influenced by the sex hormone imbalance.</p>