The aim of my pre-doctoral research is to prepare myself for a career as a NIDA-focused principal investigator oriented toward drug dependence prevention/early intervention strategies. The proposed dissertation research represents an initial step in a line of research that examines and treats clinically significant cannabis use and dependence. The first phase of this research implements and evaluates a novel, anonymous, longitudinal, web-based intervention among cannabis using and dependent young adults. Advanced statistical models will be utilized to investigate intervention outcomes. The proposed thesis research stems from the fact that cannabis dependence represents a major public health concern, and that there is a need for large-scale, low-cost intervention programs targeting young adults who use cannabis. If the thesis gives evidence of benefit from the web-based intervention, later studies that build from this thesis research step, involving other populations, will be needed and merited. Otherwise, the research must shift toward refinements of the intervention in an iterative process, until we learn more about the limiting conditions under which web interventions can be made to yield lasting benefits (e.g., as an adjunct to CBT).