This study was designed to test the effectiveness of dietary retinol in protecting the heart and lung parenchyma in a monocrotaline model for lung injury and pulmonary hypertension in rats. Male rats were assigned to three groups. Two groups were injected subcutaneously with monocrotaline (17 mg/kg body weight) and fed either the control AIN-93G diet (MC) or the control diet supplemented with retinol (17 mg retinyl palmitate/kg diet)(MR). The third group was fed the control diet and injected with the vehicle only (VC). Four weeks after monocrotaline treatment, the MR group had less thickening of the alveolar septal wall, less myocardial inflammation and degeneration of the right ventricle, and less vascular inflammation in the lung compared with the MC group. The supplemented dietary retinol, however, did not prevent development of right ventricular hypertrophy and did not affect the synthesis and secretion of surfactant phospholipids in type II pneumocytes. The results indicate that dietary retinol suppresses the inflammatory responses in the heart and lungs of rats treated with monocrotaline.