Six middle-aged (42-59 years old) and six aged (71-75 years old) subjects received each, on separate days, an oral administration of gliquidone (30 mg), glibenclamide (5 mg), gliclazide (80 mg) and glipizide (5 mg). The plasma concentration of the drugs was measured before and at eight times (60 min to 24 h) thereafter. The half-life of gliclazide was higher than that of the other three hypoglycemic agents in middle-aged subjects and was the sole to be significantly increased in aged subjects. There is no obvious difference between sulfonylureas eliminated mainly by either the kidney (glibenclamide, gliclazide, glipizide) or the liver (gliquidone) in terms of the influence of aging upon their clearance.