Phase IV studies are required as a condition of market approval. The companies look at venturing into Post marketing studies to improve the potential of the marketed product. This Phase has been the fastest growing segment in the area of clinical research. It supports in finding data for newer indications and new markets for which the drug product had not been initially approved. These studies should be randomized and to maximize the informational value. The Phase IV research environment is driven by the varying regulatory environment, increasing safety concerns of new medicines, and the need for real-world data on the marketed drugs. This paper gives an overview of the Phase IV studies which form an integral part of the drug evaluation process and is a promising phase of advancement in the area of marketed drugs.