Industrial workers on rotating shifts were evaluated for the effects of rotating shift work. Twenty-five (86%) of 29 workers in the study area who work 12-hour shifts in a scheduled 16-day rotation participated. The mean number of hours of sleep at home after working day shifts (5.6 hours) was less than after the first three night shifts (6.0, 6.4, and 6.6 hours, respectively). At work, the mean number of hours at reported peak alertness was greater during the night shift (6.1 hours) than the day shift (4.9 hours), but the perceived alertness levels were relatively lower on the night shift. Increased perceived difficulty working and decreased perceived productivity and safety were reported on the first night of the night shift. We demonstrate that workers on rotating shift work exhibit low alertness-related outcomes on both shifts. These workers have early shift work starting times that appear to disrupt sleep patterns on both day and night shifts. At this work site, a number of interventions to lessen the effects of rotating shift work are being evaluated.