Dimethylamylamine (4-methylhexan-2-amine, DMAA) is a stimulant commonly found in athletic training or pre-workout supplements. A number of commercially available products containing DMAA have been marketed as exercise boosters, promoting weight loss, or acting as an appetite inhibitor. DMAA is an aliphatic amine, with structural and pharmacological similarities to other sympathomimetic amines like tuaminoheptane (1-methylhexylamine). DMAA and tuaminoheptane are structural isomers, central nervous system stimulants, and are both included on professional and amateur sports prohibition lists such as the World AntiDoping Agency (WADA).[1–7] DMAA was originally developed in the 1940s by Eli Lilly, who commercially advertised it as the nasal decongestant Forthane.[2,4,8–10] Although Forthane was later removed from the market, DMAA eventually resurfaced as a dietary supplement in the 2000s, not long after the US ban of ephedrine.[9,11–13] For DMAA to qualify as a natural supplement, a single study was used to claim that it originated from geranium extracts, but this study is now widely debunked and no substantive evidence exists that DMAA occurs in nature.[3,14] In fact, in a study by Zhang et al., the presence of DMAA was not established in multiple geranium products, and the stereoisomeric compositions of DMAA in synthetic standards and commercial supplements were indistinguishable, confirming that DMAA cannot be considered a dietary supplement as defined by the Dietary Supplement Health and Education Act.[14] DMAA does not currently have any recognized medical use and the substance is banned or restricted in a number of countries. Since its introduction as a nutritional supplement, DMAA use has been controversial. DMAA was detected in multiple routine athletic drug testing programmes in which it is prohibited, resulting in the athletes being banned from competition,[3,8,9,14] More importantly, DMAA has been implicated as contributing to severe adverse effects and/or death on numerous occasions.