Relationships between frequency and quantity of marijuana use and last year proxy dependence among adolescents and adults in the United States1Work on this manuscript was partially supported by research grant DA09110 (Denise Kandel, principal investigator) and a research scientist award (DA00081) to Denise Kandel from the National Institute on Drug Abuse. Partial support for computer costs was provided by Mental Health Clinical Research Center Grant MH30906 from NIMH to the New York State Psychiatric Institute. Selected results were presented at the `Symposium on Marijuana Use: Basic Mechanisms, Epidemiology, Natural History, and Clinical Issues' at the annual meeting of the Committee for Problems of Drug Dependence, Puerto Rico, June 24, 1996.1