He devised the
Klein Sexual Orientation Grid, a multi-dimensional system for describing complex sexual orientation, similar to the "zero-to-six" scale
Kinsey scale used by
Alfred Kinsey, but measuring seven different vectors of sexual orientation and identity (sexual attractions, sexual behavior, sexual fantasies, emotional preference, social preference, lifestyle and self-identification) separately, as they relate person's past, present and ideal future. Klein published
The Bisexual Option: A Concept of One Hundred Percent Intimacy in 1978, based on his research. He also co-authored
The Male, His Body, His Sex in 1978. Klein moved to
San Diego in 1982. He published
Bisexualities: Theory and Research in 1986. In 1998 he founded the
American Institute of Bisexuality (AIB), also known as the Bisexual Foundation or the Bi Foundation, to encourage, support and assist research and education about bisexuality. Klein also founded the
Journal of Bisexuality. He remained the Journal's principal editor until his death. He published
Bisexual and Gay Husbands: Their Stories, Their Words in 2001. Klein published a novel,
Life, Sex and the Pursuit of Happiness in 2005. In 2006 Klein was diagnosed with cancer, and underwent surgery as a result. On May 24 of that year, he died from a heart attack at his home in San Diego, aged 73. He was survived by two brothers and his life partner, Tom Reise. Klein
donated his body to science. ==References==