A 17-year-old male presented with nephrotic syndrome associated with microscopic hematuria. Renal biopsy showed only minor glomerular abnormalities (light microscopy). Immunohistology demonstrated strong mesangial deposition of IgA. Electronmicroscopy disclosed widespread effacement of foot processes in combination with isolated osmiophilic mesangial deposits. The patient responded to standard corticosteroid therapy with complete disappearance of proteinuria. Microscopic hematuria, however, persisted. Five months after steroid therapy was stopped, the nephrotic syndrome relapsed. It was again steroid-responsive with persisting microhematuria. From clinical and morphological data we conclude that the patient has concomitant idiopathic nephrotic syndrome (minimal change glomerulonephritis) and mesangial IgA glomerulonephritis. The simultaneous presence of these two diseases may give some hint as to their pathogenesis. In both, abnormalities in T cell regulation have been found. If these were indeed involved in the pathogenesis of the two glomerular diseases, a higher than expected probability for the two entities to coexist in the same patient is to be expected.