Abstract: Image enhancement is the way toward changing digital images with the goal that the outcomes are progressively reasonable for show or further image analysis. For instance, we can remove noise, sharpen, or brightness of an image, making it simpler to distinguish key highlights. The aim of image enhancement is to improve the interpretability or perception of information in images for human viewers or to give better contribution for other automated image processing techniques. In past few decades different types of image enhancement methods have been developed by various groups of researchers. One such class of image enhancement methods is ‘adaptive gamma correction’ (AGC) based methods. In these types of methods each intensity value of given digital images is enhanced by modifying it using a power of gamma. The value of variable gamma is calculated by considering various properties of given digital image. In this paper we are going to provide a systematic review on various AGC methods. Keywords: Adaptive gamma correction (AGC), cumulative distributed function (CDF), Contrast Enhancement (CE).