Simple, precise, rapid and accurate methods for simultaneous determination of Atazanavir (ATV) and Ritonavir (RTV) in combined tablet dosage form have been developed. Method A is based on Ratio spectra derivative and method B uses integrated area under curve (AUC), methanol is used as solvent for both the methods. The amplitudes at 280.01nm and 286.12nm of the first derivative of ratio spectra were selected to determine ATV and RTV, respectively by ratio derivative method and wavelength ranges of 246.97-252.03nm and 240.78-244.16nm were selected to determine ATV and RTV by AUC method in combined formulation. Beer's law is obeyed in the concentration range of 15-75$\mu$g/mL and 5-25$\mu$g/mL for atazanavir and ritonavir, respectively by both the methods. The % assay in commercial formulation was found to be in the range 98.81-100.8% for ATV and 98.91-101.2% for RTV by the proposed methods. The methods were validated with respect to linearity, precision and accuracy. Recovery was found in the range of 99.20-99.96% for ATV and 99.12-99.97% for RTV by ratio derivative method and 99.08-99.66% for ATV and 99.78-100.6% for RTV by AUC method. The methods developed are simple, economical, precise and accurate and can be used for routine quality control of analytes in combined tablets.