The first drug to be found useful in suppressing appetite was amphetamine (Lesser and Meyerson, 1938). Amphetamine has potent central stimulant, cardiovascular, hyperthermic and anorectic properties, to all of which tolerance develops upon repeated use. The need for a more selective anorectic drug without the dangers of abuse and toxicity prompted numerous studies into the anorectic activity of a number of related compounds, all based upon the phenethylamine molecule. This led to the development of fenfluramine l-(3-trifluoromethylphenyl)-2-ethylaminopropane (Alphin et al., 1964). Fenfluramine provided the appetite suppression characteristic of amphetamine without producing the central stimulation