Background: The Australian state of Victoria has run a population-based skin cancer prevention program called SunSmart since 1988, incorporating substantial public education efforts and environmental change strategies. Trends over 15 years in behavioral risk factors for skin cancer were examined in a population exposed to the SunSmart program. Whether outcomes were associated with extent of SunSmart television advertising was then assessed. Methods: In nine cross-sectional surveys from 1987 to 2002, 11,589 adults were interviewed by telephone about their sun exposure and sun protection during outdoor activities on summer weekends. Analyses completed in 2007 adjusted for ambient temperature and ultraviolet radiation. Results: Sun protection and sunburn show substantial general improvement over time, but have stalled in recent years. Use of hats and sunscreens significantly increased over time and peaked during the mid to late 1990s, compared with the pre-SunSmart baseline. The mean proportion of unprotected skin was reduced and was lowest in the summer of 1997-1998. Summer sunburn incidence declined over time and was 9.1 in 2002, almost half baseline (OR=0.53; 95 CI=0.39-0.73). Higher exposure to SunSmart advertising in the 4 weeks before the interview increased: (1) preference for no tan, (2) hat and sunscreen use, and (3) proportion of body surface protected from the sun. Conclusions: The general improvement in sun-protective behaviors over time highlight that a population s sun-protective behaviors are amenable to change. Population-based prevention programs incorporating substantial television advertising campaigns into the mix of strategies may be highly effective in improving a population s sun-protective behaviors.