A glomerular lesion identical to that of IgA nephropathy was demonstrated unexpectedly in a 17 year old boy who presented with clinical manifestations of pulmonary hemosiderosis and with no evidence of renal disease. This subclinical glomerular lesion would have remained undetected in this patient unless kidney tissue was obtained and examined by immunofluorescence or electron microscopy. It is unknown if the glomerular lesion in this case is causally related to pulmonary hemosiderosis.