Purpose: A secondary analysis of 2000 and 2004 Indiana Youth Tobacco Survey (IYTS) data was conducted to investigate salient environmental and perceptual correlates of adolescents' current and established smoking while controlling for demographic variables such as gender, grade, and race/ethnicity and to compare the pattern of significant correlates between the years. Methods: The IYTS was an anonymous school-based survey regarding tobacco use; familiarity with pro- and anti-tobacco media messages; exposure to environmental tobacco smoke (ETS); minors' access to tobacco products; and general knowledge, attitudes, and beliefs about tobacco. In 2000, a representative sample of 1416 public high school students in grades 9-12 and 1516 public middle school students in grades 6-8 (71.44% and 72.53% response rates, respectively) were surveyed. In 2004, 3433 public high school students and 1990 public middle school students (63.04% and 65.44 % response rates, respectively) were surveyed. Results: Significant predictors of adolescents' current and established smoking habits included exposure to ETS either in homes or in cars, exposure to pro-tobacco messages, perceived benefit of smoking, and perceived peer acceptance of smoking. The influence of exposure to pro-tobacco messages greatly outweighed exposure to any anti-tobacco messages. Conclusions: The findings of this study warrant that more efforts and resources be placed on preventing youth from being exposed to ETS, and to control pro-tobacco marketing and improve the tobacco counter-marketing messages. The perceived benefits of smoking found here indicate that smoking for relaxation and weight control may be major influencing factors on adolescent smoking. (Contains 6 tables.)