In 1979 Green was a founding committee member of the Harry Benjamin International Gender Dysphoria Association and served as president from 1997 to 1999. He previously directed the human sexuality program at the State University of New York at Stony Brook. He was at various times Professor of Psychiatry at the University of California, Los Angeles, Professor of Psychiatry at the State University of New York at Stony Brook, and Professor of Psychological Medicine, Imperial College, London. He was on the faculty of Law at UCLA and Cambridge. He was made a Fellow of the Royal College of Psychiatrists in 1994. Green served as President of HBIGDA, now known as World Professional Association for Transgender Health, from 1997 to 1999.