The Endicott Work Productivity Scale (EWPS) is a brief self-report questionnaire designed to enable investigators to obtain a sensitive measure of work productivity. The total score is based on the degree to which behaviors and subjective feelings or attitudes that are likely to reduce productivity and efficiency in work activities characterize the subject during the week before evaluation. The total score was found to be reliable and valid within a group of depressed outpatients and a group of nonpatients in the community. The EWPS score is related to, but not redundant with, measures of overall severity of illness and severity of depression in these samples. The EWPS shows considerable promise as an easily used, brief, and sensitive measure for assessing the effects on work performance of various disorders and the efficacy of different therapeutic interventions.