The Len Evans Collection documents the legal and social history of homosexuality in the United States and consists of information compiled as part of the Gay History Project in San Francisco ca. 1983-1984, as well as Mr. Evans' collection of "Physique" Art and Photography. Topics include McCarthyism, what Evans' calls the "gay milieu," facts about bars, literature, the homophile movement, laws and their enforcement, erotica, and sex research as it related to homosexuals. The collection has been divided into two series: Series I, Gay History Project, San Francisco (1941-1994),  and Series II, "Physique" Art and Photography (1949-1996).

Series I, Gay History Project, San Francisco, consists of materials gathered during the course of that project (ca. 1983-1984). These materials were arranged topically in binders and include information on several facets of gay life in America. These include censorship, public opinion, and security, which includes government surveillance as well as those listed above. There is a small amount of material relating to Evans' work with the Peace and Freedom Party in the 1960s. Materials are arranged alphabetically.

Series II, "Physique" Art and Photography, consists of photographs and illustrations depicting the male form. Many of these images depict full-frontal nudity. This series also includes a written history of "Physique" photography compiled and written by Mr. Evans.