The article consists of brief review on Simultaneous equation method (Vierodt’s method). This method is applicable for estimation of those drugs whose spectra overlap properly I.e. If a sample contains two absorbing drug each of which absorbing at λmax of the other, it is possible to determine both drugs by technique of simultaneous equation method. This article consists of the list of various combined dosage form and food sample analyzed by Vierodt’s method with its wavelength, linearity range and choice of solvents. This method permits simple, rapid and direct determination of combined dosage form without prior separation and therefore can be used in routine analysis. Quantitative estimation is necessary before introduction of any drug into the market because if concentration is more in formulation it can lead to toxicity problem or if concentration is found less, then formulation will not be effective in prescribed dose.