There are a variety of methods whereby pharmacotherapy can induce weight loss. These include reducing food intake, impairing absorption of nutrients, inhibiting lipid biosynthesis and increasing energy expenditure. Various drugs are currently being evaluated which exert these modes of action. There are a large number of existing thermogenic drugs, though for one reason or another, they do not appear to be of practical value in the management of obesity. Three novel agents are BRL 26830A, LY 104 119 and RO 16-8714. These agents are chemically similar and all have lipolytic effects particularly in brown adipose tissue. BRL 26830A has been evaluated in man with conflicting results. The possible advantages and limitations of thermogenic agents in human obesity are discussed. Although the animal results are encouraging, it is advisable to take a cautious view regarding their therapeutic potential.