Unilateral pulmonary edema is uncommon and is usually associated with prolonged surgical procedures or rapid evacuation of a hydro- or pneumothorax. Unilateral pulmonary edema due to left heart failure in the absence of known lung disease is rare. It is therefore not readily recognized and is often confused with other unilateral alveolar or interstitial infiltrates. We describe 2 patients, a 69-year-old man and a 78-year-old woman, who had repeated episodes of unilateral pulmonary edema due to left heart failure. In both cases several other diagnoses were considered, but the cardiac origin of the infiltrates was supported by the rapid clearing of the lung after diuretic therapy. Awareness of this unusual clinical condition is important for the early institution of proper therapy.