To clarify the efficacy of antiobesity drugs, this article reviews all long-term (> or =36 weeks), placebo-controlled trials of obesity pharmacotherapy published since 1960. Since fears of anorexiant-induced heart valve damage preclude many physicians and patients from even considering antiobesity drugs, this area is also reviewed in-depth. Electronic database and manual bibliography search was used to identify all relevant publications. While existing studies are too few and heterogeneous to warrant meta-analysis, their review does provide evidence highly relevant to the safety and efficacy of available anorexiants. Weight loss attributable to obesity pharmacotherapy (ie, in excess of placebo) in trials lasting 36 to 52 weeks was 8.1% or 7.9 kg for those receiving phentermine resin, 5.0 % or 4.3 kg for those receiving sibutramine hydrochloride, 3.4% or 3.4 kg for those receiving orlistat, and -1.5% or -1.5 kg for those receiving diethylpropion hydrochloride. Physiologic, pathologic, and epidemiological studies strongly support that anorexiant-induced valvulopathy is attributable to specific serotonergic properties of the fenfluramines that are not present with available weight loss drugs.