The influence of two sulfonylureas on blood glucose and plasma immunoreactive insulin (IRI) and C-peptide responses to a standardized meal was investigated in a patient with type 2 diabetes and a liver disease with enhanced peripheral levels of liver enzymes. The very high fasting values of plasma IRI and C-peptide were further elevated by the meal. This response to the meal was markedly enhanced by both sulfonylureas, glipizide and glibenclamide. The blood glucose increment after the meal was diminished by sulfonylureas. Sulfonylureas thus seem to have beneficial effects in this diabetic patient, who had a liver disease and markedly elevated basal levels of plasma IRI and C-peptide concentrations.