The use of alcohol and other drugs by employed adults represents an important social policy issue because it can undermine employee health and productivity. Although national data exist regarding the overall level of alcohol and drug use among employed adults in the U.S., much less is known about the prevalence of alcohol and drug use on the job and the physical and social availability of alcohol and drugs at work. This study addressed several key issues. First, the prevalence and distribution of workplace substance use and workplace availability was explored. Second, a model of the relating overall and workplace substance availability to overall and workplace substance use was tested. Third, a “correspondence model” of employee substance use and productivity was tested. Finally, the relationship of exposure to coworkers' on-the-job substance use to the performance and morale of individuals who did not use alcohol or drugs at work was examined. The study methodology included a national telephone survey of a representative sample of 3,500 employed adults. Funded by a grant of $1,399,892 from NIAAA. 2000-2004.