Previous research has documented the relationship between the early onset of marijuana use and the increased risk of drug taking behaviors (DuRant, Smith, Kreiter, and Krowchuk, 1999; Lynskey, Heath, Bucholz, Slutske, Madden, Nelson, Statham, and Martin, 2003). The age that signifies early onset of marijuana use is not well established. Lynskey et al chose marijuana use before the age of 17. Durant et al chose the age of 11 to indicate early onset of marijuana use. The Youth Risk Behavior Surveillance System uses 13 as an established measure for onset of drug taking behaviors. The researcher chose to use the YRBSS age system to incorporate national comparisons into the research. The Center for Disease Control (YRBS, 2005) reports that 8.7% of students initiated marijuana use before the age of 13. The aim of this study is to further explore the relationship between early marijuana use (before age 13) and self reported participation in alcohol, tobacco, and other drug use. The participants were 3583 high school students who completed a modified version of the Youth Risk Behavior Survey (2003). The modified survey contains 108 questions. Onset of marijuana use was established by the students' response to the questions “How old were you when you tried marijuana for the first time”. Comparisons were made to 46 questions concerning drug, alcohol, and tobacco use. The data was analyzed using cross tabulations and odds ratios. Comparisons were made between student that reported initiating marijuana use before the age of 13 and those that had never smoked marijuana. Additional comparisons were made between those that reported the initiation of marijuana use before the age of 13 and those that reported marijuana use during or after the age of 13. Students that reported marijuana use before the age of 13 were 99 times more likely to report lifetime cocaine use than those that abstained from marijuana. Additionally, students that reported marijuana use before the age of 13 were 78 times more likely to report lifetime ecstasy use than those that abstained from marijuana. Students that initiated marijuana use before 13 were 7.7 times more likely to report lifetime cocaine use and 9.6 times more likely to report lifetime ecstasy use than those that reported initiating marijuana use during or after the age of 13. This research supports the association between the early onset of marijuana use and increased risk of drug taking behaviors. Keyword(s): youth-at-risk