The Klein Sexual Orientation Grid (or KSOG) is a system for describing a person's sexual orientation in a way that is more detailed and informative than previous methods. It was introduced by Dr. Fritz Klein (1932-2006) in the first edition of his 1978 book The Bisexual Option. It captures more nuance and complexity than the familiar, one-dimensional Kinsey Scale. Please note that the Klein Grid is not a diagnostic tool intended to test and reveal a person's sexual orientation. Instead, it is a learning tool to help people better understand the nuance and complexity that make up everyone's sexuality. In this online version, we have updated some of the language to address contemporary emphasis on identity and to acknowledge that 'gay' no longer functions as an umbrella term in the same way it did in the 1970s.