Drug discovery and traditional drug development are an expensive, time consuming, and risky business. Sometimes, these drugs are a success, while at other times, they are withdrawn, discontinued, or abandoned. Drug repurposing is regarded as a cost-effective and time-efficient method of discovering new therapeutic uses for these drugs. Due to available chemical information and preclinical safety data, the time required to develop these candidates is shorter than for newer molecular entities and costs considerably less. Further, the success rate is higher. This has resulted in many pharmaceutical companies actively directing their efforts toward drug repurposing. The following chapter discusses various strategies, approaches, barriers, challenges, and advantages of drug repurposing.