A novel, fast, sensitive, and specific capillary electrophoresis (CE) technique coupled to a diode array detector has been developed for the separation and simultaneous determination of carvedilol (CRV) and hydrochlorothiazide (HCT) in two combination formulations. The proposed method utilized a fused silica capillary (55 cm x75 microm id) and the background electrolyte solution phosphate buffer (12.5 mM, pH 7.4)-methanol (95+5, v/v). The separation was achieved at 30 kV applied voltage and 24 degree C. Atorvastatin (80 microg/mL) was chosen as the internal standard. The described method was linear over the range of 1-200 and 0.2-150 microg/mL for CRV and HCT, respectively. Intraday and interday RSD (n = 6) was < or =1.4%. The LOD values of CRV and HCT were 0.26 and 0.07 microg/mL, respectively. The validated CE method was successfully applied to the analysis of two commercial tablet dosage forms. Forced degradation studies were performed on bulk samples of the two drugs using thermal, photolytic, hydrolytic, and oxidative stress conditions, and the stressed samples were analyzed by the proposed method. Degradation products produced as a result of stress studies did not interfere with the determination of CRV and HCT; the assay could, therefore, be considered stability-indicating.