To provide background information, the original inventory of materials sent by Dr. Charles Ihlenfeld, and initial inventory completed by Kinsey Institute are included in addition to an inventory of books (some inscribed, some in German) and magazines donated by Dr. Benjamin.

In the 1920's, he worked with Dr. Eugene Steinach in Vienna. Under Steinach, Dr. Benjamin studied the influence of hormones on the aging process and worked to understand and apply endocrine therapy to geriatrics. He delivered many lectures and published more than 20 articles in this area.

Into the 1930's and 1940's, Dr. Benjamin worked with chemists Casimir Funk and Benjamin Harlow to isolate the first biologically potent male hormone (androsterone) from human urine. Additional publications and studies were focused in this area, and the term "gerontotherapy" was introduced in 1943. Also at this time, the application of endocrine therapy to sexological problems was being studied.

In 1935, Dr. Benjamin became licensed to practice in California and established a summer practice first in Los Angeles and then in San Francisco. In the 1950's Dr. Benjamin became one of the charter members of the Society for the Scientific Study of Sex. In addition, he published many articles addressing problems surrounding prostitution and venereal disease. In 1953, the term "transsexualism" was suggested in a lecture given on Gender Role Disorientation ("Transsexualism and Transvestism as Psycho-Somatic and Somato-Psychic Syndromes" was published in the American Journal of Psychotherapy in April 1954). Also in 1954, Dr. Benjamin sat on the Advisory Board of Sexology Magazine.

In 1964 Dr. Benjamin published the book Prostitution and Morality in collaboration with R. E. L. Masters (Julian Press). In 1966, he published The Transsexual Phenomenon, the first book on transsexualism (Julian Press). Contributing authors include Richard Green, M. D., Gobind Behari Lal, Ph.D., and R. E. L. Masters.

Dr. Benjamin remained in private practice in both New York and San Francisco until 1974 when he retired.

This collection consists of approximately 1500 archival folders, photographs, and slides divided into five series.

Series I: Organizational Affiliation. This series consists of minutes, pamphlets, and other ephemera arranged by HB, filed by the organization's name.

Series II: MS – Personal / Biographical / Historical. This series consists of newspaper clippings, diaries and correspondence. It also includes miscellaneous items such as personal effects.

Series III: Clinical/Research. This series consists of three parts: Patient Files (patient records, patient listings, chromosomal charts, and minutes from male and female TS meetings), Research files, and Text related to HB's research and work.

Series IV: Multi-Media. This series consists mainly of photographs, slides, and audio-cassette tapes.

Series V: Publications. This series consists of two parts: Materials related to HB's published texts, as well as off-prints and reprints of HB's articles.

Series VI: Additional Materials. This series consists of all materials donated to the institute after 1999. This series has seven sub-series, organized by date of donation from Dr. Charles Ihlenfeld or Dr. Leah Schaefer.