The Epworth Sleepiness Scale (ESS), which asks patients to estimate the likelihood that they would doze off or fall asleep in sedentary situations, has been proposed to be a quick, inexpensive way to assess sleepiness. We analyzed relations among ESS scores, mean sleep latencies on the Multiple Sleep Latency Test (MSLT), and subjective assessments of severity of sleepiness in 60 patients (34 women) with suspected excessive daytime sleepiness. Mean scores were 14.2 +/- 5.9 on the ESS and 8.3 +/- 5.2 minutes on the MSLT. ESS scores correlated negatively, but not strongly, with MSLT scores (rho = -0.37, p = 0.0042) and ESS scores of 14 and above predicted a low mean sleep latency on the MSLT. The ESS score correlated with the degree to which patients complained of sleepiness and may be useful as an otherwise elusive link between patients' complaints and their objective findings on MSLT.