Ten patients with severe pulmonary hypertension due to Toxic Oil Syndrome underwent cardiac catheterization to analyse the acute effect of intrapulmonary injection of 1.25 mg of enalaprilat. Haemodynamic parameters were obtained at basal state, 15, 30, 45 and 60 minutes after administration of the drug. Enalaprillat did not produce any statistically significant changes in pulmonary pressures and resistances or cardiac output. This lack of response is unknown but may be related to the presence of endothelial damage and fixed pulmonary vascular lesions observed at autopsy in three patients.