The objective response is an important endpoint to evaluate clinical activity of new anticancer drugs. Standardized criteria for evaluating response are needed for comparing results of different trials and represent the basis for advances in cancer therapy. Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 are the most used in clinical practice and in clinical trials; however, they are not able to capture atypical responses seen with immunotherapy drugs. We describe the evolution of response criteria with a special focus on the immune-related criteria.