Psychometric performance of the Epworth Sleepiness Scale (ESS) has not been evaluated in groups of workers. This study evaluated its use in a sample of 843 long-haul truckers. Interitem correlations and Cronbach's alpha were conducted. Correlation of the ESS with the sleep problems subscale of the Trucker Strain Monitor (TSM) was performed. Dimensionality was evaluated using factor analysis. Cronbach's alpha (.79) was strong. Interitem correlations were significant. A weak but significant correlation between the ESS and TSM sleep problems subscale (r = .18, p = < .001) was shown. Factor analysis yielded two factors that explained 56.2% of scale variance. The ESS performed well in the current sample. It is an inexpensive, time/cost-effective instrument. It should be considered for use in studies of workers in naturalistic settings. © 2007 Springer Publishing Company.