An efficient, sensitive, and simple method was developed for the simultaneous determination of rosiglitazone and metformin hydrochloride in a combination tablet dosage form by column high-performance liquid chromatography. The mobile phase used was ammonium dihydrogen phosphate adjusted to pH 5.25 with sodium hydroxide. The limits of detection and quantitation were in the range of 0.5-1.6 microg/mL, respectively, for metformin hydrochloride, and 0.00201-0.0067 microg/mL, respectively, for rosiglitazone. The linearity was studied in the concentration range of 0.12-0.31 microg/mL for rosiglitazone and 30.6-76.7 microg/mL for metformin hydrochloride. The recovered amounts of metformin hydrochloride and rosiglitazone were 100-103.8 and 101-103.7%, respectively.