We report a case of biopsy-proven secondary hemosiderosis of the lung in a 58-year-old patient with mitral valvular heart disease. Both chest radiography and high-resolution CT demonstrated patchy areas of ground-glass opacity ; the former indicated that it was in both lungs, while the latter showed inter-and intralobular septal thickening. These findings were reversible when pulmonary venous hypertension was corrected.