Background: The reasons for initiation and continuation of use of illicit substances are multifactorial; however, some individuals appear resistant to both. One set of determinants lies in the environment. In ongoing studies, we are examining environmental concomitants of behavior in individuals in drug treatment. In this study, we will examine environmental factors that may impact initiation, addiction, and treatment seeking among the greater population at large (non-drug-users, current opioid/stimulant users, and current marijuana users).