The document discusses the phenomenon of "chemsex" among gay, bisexual, and other men who have sex with men (MSM) in the UK. Chemsex refers to using drugs like mephedrone, GHB/GBL, and crystal methamphetamine in order to enhance sexual experiences. It has become a significant issue, leading to increased risk-taking, addiction, and rising STI/HIV transmission. The document outlines the drugs commonly used, trends observed in MSM communities and support services, and recent responses from health organizations to address chemsex and promote harm reduction.