Simple, precise, rapid and accurate methods for simultaneous determination of Lamivudine, Zidovudine and Nevirapine in combined tablet dosage form have been developed. Method is based on Ratio spectra derivative and methanol is used as solvent. The amplitudes at 229.77 nm, 316.40 nm and 341.76 nm of the first derivative of ratio spectra were selected to determine Lamivudine, Zidovudine and Nevirapine, respectively by ratio derivative method. Beer's law is obeyed in the concentration range of 6-18 $\mu$g/ml, 12-36 $\mu$g/ml and 8-24 $\mu$g/ml for Lamivudine, Zidovudine and Nevirapine, respectively by Ratio Derivative method. The % assay in commercial formulation was found to be in the range 99.01 - 100.90 % for Lamivudine, 99.3 - 101.11% for Zidovudine and 98.91 - 101.72 % for Nevirapine by the proposed method. The method was validated with respect to linearity, precision and accuracy. Recovery was found in the range of 99.36 - 100.23 % for Lamivudine, 98.91 - 101.32% for Zidovudine and 99.0 - 100.4 % of Nevirapine by ratio derivative method. The method developed is simple, economical, precise and accurate and can be used for routine quality control of combined tablets.