The effects of infusion i.v. of 0.9% sodium chloride solution, Hartmann's and 5% dextrose solution on the concentrations of circulating metabolites and insulin were compared in patients undergoing cholecystectomy. Hartmann's solution had a similar effect on the metabolic response to 0.9% sodium chloride solution, but the use of 5% dextrose was associated with an exacerbation of the hyperglycaemic response to surgery. Plasma insulin concentrations increased significantly in the group receiving 5% dextrose showing that the usual suppression of insulin during abdominal surgery can be overcome by a strong glycaemic stimulus.