Health communication campaigns intended to reduce chronic and severe exposure to ultraviolet radiation in sunlight and prevent skin cancer are a national priority. Outdoor workers represent an unaddressed, high-risk population. Go Sun Smart (GSS), a worksite sun safety program largely based on the diffusion-of-innovations theory, was evaluated in a pair-matched, group-randomized, pretest-posttest controlled design enrolling employees at 26 ski areas in Western North America. Employees at the intervention ski areas were more aware of GSS (odds ratio [OR] = 8.27, p less than 0.05) and reported less sunburning (adjusted OR = 1.63, p less than 0.05) at posttest than employees at the control areas. A dose response was evident (OR = 1.46, p less than 0.05) with greater observed program implementation associated with fewer sunburns among employees. Program awareness per se was not predictive (p greater than 0.05) of reduced sunburning in a mediational analysis. Analyses of nonrespondents, including intent-to-treat analyses, further supported the success of GSS. (Contains 2 tables and 1 figure.)