The proposed study is intended primarily to determine the effectiveness of BRL 49653C by measure of glucose homeostasis as determined by Hb A1c and fasting plasma glucose, when added to sulphonylurea therapy (sulphonylureas are limited to: glibenclamide, glipazide and gliclazide). In addition, the clinical safety of BRL 49653C will be assessed in this patient population. The starting doses have been selected based on dose response studies examining safety, tolerability and efficacy in the U.S.A.