Marijuana is the most commonly used illicit substance in the U.S. In the state of Colorado, rates of marijuana use are among the highest in the nation, with at least 25% of young adults reporting use within the last month. Chronic, heavy marijuana users experience significant consequences as a result of their use, including a range of health, cognitive and psychological outcomes. Considering the range of possible impairments, it is possible that marijuana use could impact the academic performance of college students and interfere with their ability to fully benefit from their academic studies. A number of studies with adolescents have demonstrated a consistent relationship between marijuana use and poor school performance. It is not clear whether marijuana use and psychological impairments would impact college success or how complex substance use dynamics may operate to impact success. One substance-related factor that often gets little attention is craving. It is possible tat greater marijuana craving could lead to more frequent marijuana use, thus impacting not only the cognitive focus of students but also their motivation for academic work. The current proposal, a collaboration among new, early-stage investigators and an established NIH investigator from several disciplines (psychology, medicine, education, and quantitative methodology), will extend initial pilot work to learn more about the association between marijuana use and craving, psychological problems, and academic performance and persistence among university students. Ecological momentary assessment (EMA), a data collection strategy that focuses on in the moment assessment of a range of target behaviors, will be used as the primary method of data collection due to its increased accuracy compared to retrospective or prospective approaches. Over a three-year time period, we propose to assess 150 university students who are using marijuana at least weekly or greater. Participants will complete baseline measures and a two-week EMA protocol using SMS texting. A review of participants' academic records will take place at the end of the semester of their baseline participation and one full semester after the initial visit to examine university attrition. We hypothesize that marijuana craving and mood will predict subsequent marijuana use when assessed through EMA. We expect to find relationships between a range of psychological impairments (e.g., depression, anxiety), personality traits and students' marijuana use and academic performance.