We examined the pulmonary hemodynamics and morphology after injection of a sclerosing solution of 5% ethanolamine oleate (EO) into 24 normal dogs. EO of 0.5 ml/kg (n = 5), 1.0 ml/kg (n = 6), and 3.0 ml/kg (n = 7) was injected through the jugular vein into the right atrium for pathological examination and gravimetric study of the lung, while monitoring the pulmonary hemodynamics for 12 h. Normal saline of 3.0 ml/kg was injected into the remaining 6 control dogs, using the same method. Cardiac output significantly decreased immediately after injection of the sclerosant in all dogs given 0.5 ml/kg, 1.0 ml/kg and 3.0 ml/kg injections of EO; however, there was a tendency toward recovery from 6 h after injection in dogs given 0.5 ml/kg and from 9 h in dogs given 1.0 ml/kg. Pulmonary hypertension just after injection and hypoxia at 9-12 h occurred only when 3.0 ml/kg was injected. Irreversible pulmonary hemorrhage was present in the excised lungs in 4 of 7 dogs given 3.0 ml/kg, while there were no significant lesions in the other dogs. The lung water content in cases of 1.0 and 3.0 ml/kg injections was significantly higher than that in the controls, while there was no significant difference between those given 0.5 ml/kg and of the controls. The findings obtained in this study suggest that EO less than 0.5 ml/kg used for sclerosing esophageal varices seems to have little untoward influence on pulmonary hemodynamics and morphology.