Serenoa repens (Permixon) has been available for several years for the treatment of men with benign prostatic hyperplasia (BPH). The drug is the n-hexane lipidosterolic extract of the dwarf American palm (also known as Serenoa repens) and is a complex mixture of various compounds. A number of pharmacodynamic effects have been demonstrated with the lipidosterolic extract of Serenoa repens (LSESR), suggesting multiple mechanisms of action including in vitro inhibition of both type 1 and type 2 isoenzymes of 5 alpha-reductase and interference with binding of dihydrotestosterone to cytosolic androgen receptors in prostate cells. In controlled clinical trials in men with BPH, oral administration of Serenoa repens 160 mg twice daily for 1 to 3 months was generally superior to placebo in improving subjective symptoms, such as dysuria, as well as objective parameters. The frequency of nocturia was reduced by 33 to 74%, while urinary frequency during the day decreased by 11 to 43% and peak urinary flow rate increased by 26 to 50% with Serenoa repens. Corresponding values for placebo were 13 to 39%, 1 to 29% and 2 to 35%. The only large comparative trial conducted to date, in which > 1000 men with moderate BPH were randomised to receive Serenoa repens 160 mg twice daily or finasteride 5 mg once daily for 6 months, demonstrated similar efficacy between the two drugs. No statistically significant difference was demonstrated between treatment groups for improvement in patient self-rated quality-of-life scores and the primary end-point of objective symptom score; International Prostate Symptom Score improved by 37% with Serenoa repens compared with 39% with finasteride. In much smaller comparative trials, few significant differences were demonstrated between Serenoa repens and alpha 1-receptor antagonists, and larger randomised trials of adequate duration are required to better compare the clinical efficacy of these drugs. The most frequently reported adverse events in clinical trials with Serenoa repens have been minor gastrointestinal problems (e.g. nausea and abdominal pain). In conclusion, Serenoa repens is well tolerated and has greater efficacy than placebo and similar efficacy to finasteride in improving symptoms in men with BPH. Although there is a need for further comparative studies, particularly with alpha 2-receptor antagonists, available data indicate that Serenoa repens is a useful alternative to alpha 1-receptor antagonists and finasteride in the treatment of men with BPH.