When compared with values recorded in 14 control subjects, the 15 overweight patients with type 2 diabetes displayed significantly increased activities of serum alanineaminotransferase (172% of mean values in controls), gamma-glutamyltransferase (253%) and cholinesterase (139%). A much wider dispersion of individual values for the two firstly mentioned enzymes was however noted so that their correlation with serum triglycerides levels were weaker (r = 0.373; p < 0.05 and r = 0.451; p < 0.05 respectively) than the same correlation obtained for serum cholinesterase (r = 0.760; p < 0.001). In two other studies including 28 controls and 30 diabetic patients serum cholinesterase was found to be significantly correlated with serum levels of insulin (r = 0.622; p < 0.001), C-peptide (r = 0.652; p < 0.001) and free fatty acid (r = 0.821; p < 0.001). Circumstantial evidence is provided that insulin resistance and an increased flux of free fatty acids from adipose tissue to the liver would stimulate the hepatic synthesis of serum cholinesterase.