1. Vasodilators are currently under investigation as possible therapeutic agents in the treatment of portal hypertension. Among them calcium-channel antagonists and organic nitrates have been of particular interest. Few and conflicting data, however, have been reported on their effect on liver function. 2. Twenty patients with biopsy-proven alcoholic cirrhosis were studied before and 25-35 min following the acute administration of 5 mg verapamil i.v. (eight patients) or 5 mg isosorbide dinitrate sublingually (12 patients). The plasma clearance of indocyanine green (ICG) and its intrinsic hepatic clearance were used as indices of liver function. Seven further patients were investigated before and after a placebo infusion according to the same methodology. 3. No significant change in ICG kinetics was found after verapamil or isosorbide dinitrate.