Recent investigations of the role of large infusions of concentrated serum albumin on the acute pulmonary edema caused by hydrochloric acid (HCl) aspiration have produced contradictory results. We used the open thorax anesthetized dog with weighed lung lobe as well as completely isolated perfused weighed lobes. The results were the same with both preparations. Instillation of 0.1 N HCl (2 ml/kg) caused small increases in pulmonary artery pressure, and the rate of lung weight gain increased from 1.2 to 2.5 g/h to 22.2 to 30.2 g/h. Addition of 25% human serum albumin, either before or after acid instillation, had no significant effect on the rate of lobe weight gain. Additional experiments showed that after HCl the rate of lobe weight gain was exquisitely sensitive to pulmonary arterial pressure. Albumin therapy is without benefit in the prevention or treatment of the pulmonary edema caused by HCl aspiration.