In this thesis, derivative spectrophotometric and multivariate method of assaying truvadaÂ®rncombination tablets, which contain tenofovir disoproxil fumarate 300 mg, and emtricitabine 200rnmg, is described. Emtricitabine, 4-amino-5-fluoro-1-[2-(hydroxymethyl)-1,3-oxathiolan-5-yl]-rnpyrimidin-2-one, and tenofovir DF, 1-(6-aminopurin-9-yl)propan-2-yloxymethylphosphonicrnacid, are anti-HIV drugs of nucleoside / nucleotide reveres transcriptase inhibitor class.rnEmtricitabine was determined at 294.5 nm using the "zero crossing" technique because thernsignals of tenofovir DF is zero at this wavelength. Tenofovir DF was determined at 270.5 nm byrnthe same technique because emtricitabine have no contribution at this wavelength. Tenofovir DFrnwas quantified at 249.5nm and 270.5 nm wavelengths by using derivative ratio techniquernbecause the signal of emtricitabine was zero at these wavelengths. Emtricitabine was quantifiedrnat 288.5 and 303.5 nm because the signal of tenofovir DF was zero at these wavelengths. Byrnclassical least square (CLS) and principal component regression (PCR) methods goodrnreproducible and repeatable results were obtained. In choosing the optimal magnitudes for thernsimultaneous determination of both drugs, the following criteria were considered: the linearity,rnthe intercept, the sensitivity, the degree of interference, the relative percent error, the relativernrecovery, and the reproducibility. The R2 values which are in excess of 0.999, which indicatedrnthe good linearity of the calibration graphs. Sample recovery rates were found satisfactoryrn(almost all are > 99%) with relative standard deviations (RSD) of less than 5%. The mentionedrnchemometrics-assisted techniques were successfully applied to simultaneous determination ofrnemtricitabine and tenofovir DF in the laboratory-prepared mixtures and commercial tablets withrnconsiderable precision and good recoveries.