Simple multivariate spectrophotometric procedure for simultaneous determination of levofloxacin and norfloxacin as representative examples of fluoroquinolones and their decarboxylated degradation products is described. The method is based on the spectrophotometric measurements of the studied drugs and their degradants in 0.1 M hydrochloric acid solutions in the general range of 200-370 nm together with multivariate calibration analysis. The components of mixtures composed of either levofloxacin or norfloxacin and the corresponding degradant. show a considerable degree of spectral overlapping (85.1-87.4%). Resolution of the binary mixtures under investigation has been accomplished mainly by using classical least squares (CLS) analysis. The method is applied successfully for determination of each drug in pure form, laboratory prepared degraded samples and in expired commercial dosage forms and good recoveries were obtained. Results were compared to those obtained by reported procedures for the same combinations and the required statistical parameters were calculated. The degradation rates for the studied drugs at 150° in 2 M HCl were also studied using the proposed procedure. The calculated first order rate constants for the decarboxylation of the studied drugs were found 0.109 and 0.082 hour-1 and the t1/2 were 6.32 and 8.50 hours for levofloxacin and norfloxacin respectively