Behcet's disease is a multisystem disorder characterized by oral and genital ulcers, uveitis, and skin lesions. Renal involvement has rarely been observed in Behcet's disease. However, pathological reports have revealed various lesions, especially, amyloidosis, focal and segmental glomerulonephritis with crescents, and IgA nephropathy. A 49-year old female with Behcet's disease was admitted to evaluate proteinuria and microscopic hematuria, and renal biopsy showed IgA nephropathy (subclass V). Immunohistology revealed mesangial deposits of IgA and staining for C3. We report a case of IgA nephropathy which was diagnosed by renal biopsy in a patient with Behcet's disease.