He retired from the active practice of internal medicine in 1998 after thirty-seven years. Cassell is the author of The Healer's Art, The Place of the Humanities in Medicine, Changing Values in Medicine, two volumes on doctor-patient communication entitled Talking with Patients and Doctoring: The Nature of Primary Care Medicine, The Nature of Healing, and The Nature of Suffering and the Goals of Medicine, now in its second edition. Cassell is a Fellow of the Hastings Center, Member of the Institute of Medicine of the National Academy of Sciences, and Master of the American College of Physician.