Ultraviolet radiation is the most important carcinogenic agent related to the development of melanoma and nonmelanoma skin cancer, and primary prevention efforts focus on reducing exposure to sunlight and ultraviolet sunlamps. Favorable societal views of suntanning serve as an obstacle to skin cancer prevention. Although the education of patients and the public regarding the risks of excessive ultraviolet light exposure is an important goal in medicine today, few physicians have more than a vague knowledge of how current attitudes actually developed during the past century. Opinions about ultraviolet light exposure were not static, but evolved with increasing scientific knowledge and changing social mores. A critical interplay occurred between the prevailing medical and nonmedical views on the subject. In this article, we focus on the century's start (1900-1920)--a time when vigilance against significant sun exposure, a relic of the 19th century, was eroding, and the roots of later attitudes toward sunbathing were already manifest. Medically, the view of sunlight as salutary was bolstered by the success of phototherapy, which was introduced in the 1890s. The first clinical observations associating long-term sunlight exposure with skin cancer were also reported during this time. The association, however, was poorly understood, and this work was largely ignored by the medical profession and remained essentially unknown to the public.