Chemoprevention, the use of drugs to prevent invasive neoplasia, has gained increasing significance in recent years. Especially for the skin, chemoprevention will become of importance, because large areas of the skin are exposed to environmental carcinogenic factors. Furthermore, many skin diseases predispose to the development of multiple skin tumors. One group of chemopreventive agents are the retinoids, which are effective modulators of cell proliferation and differentiation in normal as well as in transformed tissues. Though the mechanism of action of retinoids is not yet fully understood at the molecular level, chemoprevention studies have demonstrated the ability of retinoids to prevent the development of skin cancer, particularly in patients with xeroderma pigmentosum, multiple basal cell carcinoma and oral leukoplakia. A better understanding of the carcinogenic process should improve our ability to develop effective chemoprevention strategies.