An HPLC procedure for the simultaneous determination of metformin in combination with glipizide and gliclazide in pharmaceutical preparations is described. A Zorbax XDB C 18 15 cm analytical column and UV detection at wavelength 226 nm were used. In this study, various mobile phase variables were studied to determine the effects that each had on metformin, glipizide, and gliclazide. The reproducibilities in combination I for metformin and glipizide were 1.39%, 1.30%, and in combination II for metformin and gliclazide were 1.28%, 1.75%, respectively.The determinations of glipizide, metformin (combination I), and gliclazide, metformin (combination II) gave recoveries with respect to the values declared by the manufacturers for glipizide and metformin (combination-I) in the range 96.1-103.4%, 95.0-100.0% using peak areas, and 96.4-103.6%, 97.3-102.5% using peak heights, respectively. The recoveries for the gliclazide and metformin (combination II) were in the range 94.7-100.8%, 96.2-101.2% using peak areas, and 94.3-101.5%, 97.8-102.5% using peak heights, respectively.