Employers are becoming increasingly concerned about the consequences and costs of substance use in their workplaces. Despite this heightened awareness, little information is available to guide them in setting up worksite-based prevention and assistance programs. Most estimates of the prevalence or consequences of substance use are derived from large national surveys of households or individual persons. The primary contribution of this research to the public health literature is the empirical results from a unique data set. In particular, this study presents results of a survey administered to more than 1,200 employees at five different worksites. Descriptive statistics for the prevalence of smoking, alcohol and illicit drug use, prescription drug misuse, and workplace consequences, such as reduced performance and absenteeism, are reported, as well as findings from a multivariate analysis of substance use prevalence and consequences. Compared with national averages, workers at these five sites tended to have substance use profiles similar to or slightly lower than estimates from large national surveys. The study's estimates may help employers identify the extent of a substance abuse problem in their worksites and specific areas to target for possible intervention.