For type 2 diabetes treatment, combinations of drugs from the thiazolidinedione and sulfonylurea groups are now available in the same tablet or capsule. Therefore, a stability-indicating and validated HPLC method was developed for simultaneous determination of pioglitazone, rosiglitazone, and glipizide in combined dosage forms. The examined drugs were subjected to different conditions such as acid and base, temperature, and UV light, and degradation of pioglitazone and glipizide was observed under thermal and acidic stress. However, selectivity of the presented method for pioglitazone, rosiglitazone, and glipizide assay against their degradation products was confirmed. It was also demonstrated to be robust, resisting small deliberate changes in pH of the buffer, flow rate, and percentage of acetonitrile in the mobile phase. The presented method utilizes a LiChrospher RP18 column (125 x 4.0 mm), acetonitrile in phosphate buffer at pH 4.3 (40 + 60, v/v) as the mobile phase, and UV detection at 225 nm for pioglitazonel glipizide or 245 nm for rosiglitazone/glipizide. The method was validated with respect to linearity, precision, and accuracy. Finally, the elaborated procedure was applied for the QC of pioglitazone/glipizide and rosiglitazone/glipizide mixtures.