In article number 1801363 Shiladitya Sengupta, Ali Khademhosseini and co-workers show organ-on-a-chip systems can provide high-throughput platforms for drug development, which could potentially bridge the gap between 2D cell culture and animal models. With recent breakthroughs in anticancer immunotherapies, there is an increasing interest in organotypic models for anti-cancer immunotherapy development. This study reviews current progress in cancer-on-a-chip and immune organ-on-a-chip systems with an emphasis on their potential for drug development.