He has taught anesthesiology at the University of Wisconsin - Madison and Thomas Jefferson University in Philadelphia. He has published in several medical journals including JAMA, JAVMA, Geriatrics, Pain Digest and Cardiothoracic Anesthesia. He has performed experiments on animals and research on humans. With his wife, Jean, a veterinarian, he wrote Sacred Cows and Golden Geese: The Human Cost of Experiments on Animals. The Greeks' thought-provoking letters-to-the-editor have appeared in leading newspapers across the country, and their Op/Ed pieces have sparked debate among readers both nationally and internationally.