In a randomised, comparative, parallel group study overweight diet-treated type 2 diabetic patients attending a teaching hospital in Peshawar, Pakistan, were assigned to 12 months of monotherapy with metformin (n=102) or glibenclamide (n=102) to investigate the effects of these agents on serum sialic acid (SSA). Drug treatment significantly improved glycaemic control and metformin treatment also appeared beneficial to other parameters monitored, significantly reducing triglycerides. Throughout the study SSA decreased in both treatment groups and there were no statistically significant differences between the groups. However, in the metformin-treated group SSA at 12 months was significantly lower than at baseline.