Cosmas and Damian were martyred around the year 300 A.D. in what is now Syria. Called the Anargyroi ("without silver") because they charged no fees, they became patrons of medicine, surgery, and pharmacy and the focus of cults ranging across Europe. They were popular in Byzantine and Orthodox traditions and their shrines are numerous in Eastern Europe, southern Italy, and Sicily. The Medici family of Florence viewed the "santi medici" as patrons, and their deeds were illustrated by great Renaissance artists. In medical literature they are now revered as patrons of transplantation. Jacalyn Duffin offers a profound exploration of illness and healing experiences in contemporary society through the veneration of the twin doctors Saints Cosmas and Damian. She also relates a personal journey, from her role as a hematologist who unexpectedly came to serve as an expert witness in the Church's evaluation of a miracle to her research as a historican on the origins, meaning, and functions of saints. Duffin's research, which includes interviews with devotees in both North America and Europe, focuses on how people have taken the saints with them as they moved both within Italy and beyond. She shows that veneration of Cosmas and Damian has spread beyond immigrant traditions to fill important functions in healthcare and healing. Duffin's conclusions provide essential insights into medical history, sociology, anthropology, and popular religion, as well as the current medical debate over spiritual healing. Medical Saints draws on medical history and Roman Catholic traditions, but extends to universal observations about the behaviors of sick people and the formal responses to individual illness from collectivities in religion, medicine, and history.