'Her contributions were the key to advancing the care and survival of heart transplant patients,' said Dr. Robert Robbins, director of the Stanford Cardiovascular Institute. Billingham joined Stanford in 1966, two years before Dr. Norman Shumway performed the first successful heart transplant in the United States there. To ensure the success of the transplants, it was vital to know whether the body was accepting or rejecting them. Billingham and Dr. Philip Caves devised a technique to remove tiny snippets of heart tissue and analyze them. She developed a standardized scale for interpreting biopsy results that is still used in modified form: the Billingham Scheme, also known as Billingham's criteria. She not only created it, but she persuaded the international community to adopt a similar scale, said Dr. Sharon Hunt, a professor of cardiovascular medicine. Billingham joined Stanford at a time when female physicians were a rarity at academic institutions. She was a fierce advocate for women and toward the end of her career was appointed director of women in medicine and medical sciences at Stanford. She became the first female president of the International Society for Heart and Lung Transplantation in 1990. She was born Margaret E. Macpherson on Sept. 20, 1930, in Tanga, Tanzania, where her father worked for the British government. She received her medical degree in 1954 from the Royal Free Hospital School of Medicine in London. She met her husband, Dr. John Billingham, while both were interning at Hampstead General Hospital in London, and they were married in 1956. The family immigrated to the United States in 1963. Billingham retired from Stanford in 1994, and she and her husband moved to Penn Valley in the foothills of the Sierra Nevada in Northern California, where she enjoyed gardening, fishing and exploring the state. In addition to her husband, former chief of the life-sciences division of NASA's Ames Research Center, she is survived by two sons, Robert and Graham, both of Auburn, Calif.; her sister, Shirley Ann; and four grandchildren. 