A female patient has suffered from Behçet's disease (BD) for 15 years. During one recurrent episode proteinuria and microscopic hematuria were discovered. Renal biopsy revealed focal segmental glomerulopathy with IgA deposits. Renal involvement in BD is uncommon and includes amyloidosis, crescentic glomerulonephritis and IgA nephropathy. BD is a cause of secondary IgA nephropathy. Immunologic features of the two diseases, particularly increased serum IgA, are reviewed.