1,2-Dithiole-3-thiones are five-membered cyclic sulfur-containing compounds with antioxidant, chemotherapeutic, radioprotective and cancer chemoprotective properties. One substituted dithiolethione, oltipraz [5-(2-pyrazinyl)-4-methyl-1,2-dithiole-3-thione], originally developed as an antischistosomal agent, has recently been observed to protect against chemically induced carcinogenesis in lung, trachea, forestomach, colon, breast, skin, liver and urinary bladder in rodents. The induction of electrophilic detoxication enzymes, which result in diminished carcinogen-DNA adduct formation and reduced cytotoxicity, appears to be an important component of the anticarcinogenic action of oltipraz and other dithiolethiones. Phase I trials of oltipraz are presently underway in the United States. Subsequent trials might be most appropriately targeted towards individuals at high risk for occupational or environmental exposures to genotoxic carcinogens.