PURPOSE: To review clinical data on raloxifene hydrochloride, a selective estrogen receptor modulator that was recently approved for the prevention of osteoporosis in postmenopausal women. DATA SOURCES: English-language articles published from 1980 to May 1998 were identified through MEDLINE searches. Bibliographies, book chapters, and meeting abstracts were reviewed for additional relevant publications. STUDY SELECTION: Publications that contained information on the background of development, structure, mechanism of action, tissue-selective effects, and adverse effects of raloxifene hydrochloride were included. DATA EXTRACTION: Data in selected articles were reviewed, and relevant clinical information was extracted. DATA SYNTHESIS: Raloxifene hydrochloride was developed in an effort to find a treatment for breast cancer and osteoporosis. It binds to the estrogen receptor and shows tissue-selective effects; thus, it belongs to a class of drugs recently described as selective estrogen receptor modulators. Tissue selectivity of raloxifene may be achieved through several mechanisms: the ligand structure, interaction of the ligand with different estrogen receptor subtypes in various tissues, and intracellular events after ligand binding. Raloxifene has estrogen-agonistic effects on bone and lipids and estrogen-antagonistic effects on the breast and uterus. An increase in bone mineral density at the spine, total hip, and total body has been reported with raloxifene but seems to be less than that seen with estrogen or alendronate therapy. Raloxifene has been shown to produce a reduction in total and low-density lipoprotein cholesterol concentrations similar to that produced by estrogen therapy, but high-density lipoprotein cholesterol and triglyceride concentrations do not increase during raloxifene therapy. In the uterus, raloxifene does not stimulate the endometrium. Long-term data on the effects of raloxifene in reduction of risk for fracture; prevention of cardiovascular events; cognitive function; and the incidence of breast, ovarian, and uterine cancer are not available. The most common adverse effect of raloxifene is hot flashes. CONCLUSIONS: Raloxifene has been shown to have beneficial effects in selected organs in postmenopausal women. Although estrogen remains the drug of choice for hormonal therapy in most postmenopausal women, raloxifene may be an alternative in certain groups of women at risk for osteoporosis.