Three new methods are described for the simultaneous determination of chlorphenoxamine hydrochloride (CP) and caffeine (CAF) in their combination. In the first method, ratio spectra derivative spectrophotometry, analytical signals were measured at the wavelenghts corresponding to either maxima and minima for both drugs in the first derivative spectra of the ratio spectra obtained by using each other spectra as divisor in their solution in 0.1 M HCl. In the other two methods, chemometric techniques, classical least-squares (CLS) and inverse least-squares (ILS), the concentration data matrix were prepared by using the synthetic mixtures containing these drugs in 0.1 M HCl. The absorbance data matrix corresponding to the concentration data matrix was obtained by the measurements of absorbances in the range 225-285 nm in the intervals with Δλ=5 nm at 13 wavelengths in their zero-order spectra, then, calibration or regression was obtained by using the absorbance data matrix and concentration data matrix for the prediction of the unknown concentrations of CP and CAF in their mixture. The numerical values were calculated by using MAPLE V software in chemometric methods. The procedures do not require any separation step. The accuracy and the precision of the methods have been determined and they have been validated by analyzing synthetic mixtures containing title drugs. These three methods were successfully applied to a pharmaceutical formulation, sugar-coated tablet, and the results were compared with each other. © 2002 Elsevier Science B.V. All rights reserved.