He visited the Gender identity clinic at Johns Hopkins University in the 1970s and has worked in this field since then.
He worked at from 1978 to 1992 at the Institute for Sex Research and Forensic Psychiatry at Hamburg University.
His range of research interests include Gender dysphoria, research into psychotherapy, Forensic psychiatry, and History of psychiatry.
From 1995 to 1997, he was President of the Harry Benjamin International Gender Dysphoria Association now called World Professional Association for Transgender Health.
[4][2] He was also previously the president of The International Association for Forensic Psychotherapy.