The diagnosis of pulmonary lymphangitic carcinoma usually requires fiberoptic bronchoscopy with transbronchial biopsy, percutaneous needle aspiration of the lung, and/or open lung biopsy. We performed right heart catheterization in three patients with adenocarcinoma, in whom the diagnosis of pulmonary lymphangitic carcinoma was made on the basis of cytologic examination of pulmonary capillary blood.