There is accumulating evidence that salicylate and glipizide may exert a clinically relevant interaction. Therefore, it was of interest to examine the possible interactions of glipizide and antirheumatics of non-salicylate character, e.g., phenyl propionic acid derivatives. The present report deals with the possible interaction between glipizide and indoprofen, a novel and potent antirheumatic agent. The subjects studied were 6 healthy volunteers, who took indoprofen 200 mg t.i.d. for 7 days and a single 5 mg dose of glipizide before and during indoprofen medication. Series of blood samples were obtained for measurements of indoprofen, glipizide, and glucose concentrations in blood. In addition, urine concentrations of indoprofen were determined. The concentrations of glipizide and indoprofen were measured by high-pressure liquid chromatography, and that of glucose ezymatically. The results indicate that chronic indoprofen administration may reduce glipizide concentrations in plasma, but this reduction need not lead to a major influence on the blood glucose response to glipizide.