We evaluated the role of the halogenated salicylanilides and related compounds in the development of photocontact dermatitis between 1967 and 1975 as seen at the University of California, San Francisco clinic. During this period positive photopatch tests to at least one of these chemicals were detected in 98 patients. Prior to 1967, tetrachlorosalicylanilide and the brominated salicylanilides were the most common offenders. Declines occurred in number of patients with positive photopatch tests and patch tests to these agents as well as the number of patients tested to these agents during this period; ie, almost three times as many people were tested and four times as many had positive photopatch tests in the last six months of 1967 as compared to the first nine months of 1975. The most striking reduction in numbers of patients with positive tests occurred after 1968, but the most notable reduction in the total number of positive photopatch tests occurred after 1970. We concluded that these results were most likely due to removal from the market of the more potent photosensitizing chemicals and increased physician familiarity with the disease process.