Until 1973, homosexuality was considered a mental disorder. Gays and lesbians were administered shock treatments and frontal lobotomies, and were committed to mental instituions. The work of Dr. Evelyn Hooker was a major influence in removing homosexuality from the American Psychiatric Association's Mental Disorder Diagnotic Manual. Dr. Hooker's research was most responsible for changing how homosexuals were treated by mental health providers, the medical community, government, educational institutions, and the public at large.

Dr. Hooker was a UCLA psychology professor who pioneered research on the psychology of homosexuality. Her paper, The Adjustment of the Male Overt Homosexual, published in 1957 was the first objective scientific study of gay mental health.

Through her research, Dr. Hooker demonstrated that there is no measurable psychological difference between heterosexual and homosexual men.

Dr. Hooker was "hoplessly heterosexual", as she said, but she enjoyed a deep respect for gay culture and maintained a number of lengthy gay friendships.

Dr. Hooker led the Christopher Street West Parade in West Hollywood in 1986 and received the Morris Kight Humanitarian Award from the Los Angeles Gay and Lesbian Center in 1990. In 1991 Dr. Hooker received the Award for Distinguished Contribution to Psychology in the Public Interest, presented by the American Psychological Association.

Dr. Hooker was the subject of an Academy Award nominated documentary film, Changing Our Minds: The Story of Dr. Evelyn Hooker produced by David Haugland in 1992.

In 1995, in an interview in The Blade, an Orange County gay magazine, Dr. Hooker gave the following grim warning: "I firmly believe we are in for rough times, the far right have it. I lived through the McCarthy era. Those times are coming again. The first people to be put under the scrutinizing eye will be gay people. Cherish your freedom while you have it."