A historical retrospective study of 242 shiftworker (SW) and 224 non-SW (NSW) injuries at a chemical manufacturing plant in southeast Texas (U.S.A.) was performed. Data were collected on injuries that occurred between 1 January 1982 and 31 December 1985. The SW schedule comprised an 8-hr, 7-day backward rotation program while the dayworker schedule consisted of a typical U.S.A. 40-hr work week. Injury records were matched against payroll/attendance records to substantiate the probability of isolating possible effects of the shiftwork rotation schedule on the rates, distribution and severity of injuries. Injuries in the SW sample were compared to those in the non-SW sample. The work responsibilities of dayworkers were not exactly the same as those of shiftworkers. However, the job responsibilities for males and females within the dayworker and shiftworker groups were equivalent. Overall injury incidence rates were not significantly different between SWs and non-SWs, although female SWs had significantly higher incidence rates than did male SWs and both male and female dayworkers. The occurrence of injuries, however, was not equally distributed during the day shift and the night shift, but was equally distributed during the evening shift and for non-SWs, suggesting that certain, yet to be determined, factors were affecting the distribution of injuries during the day and night shift. However, the average number of injuries was two-three times higher during the first four days of the day and night shift, yet were not elevated during the evening shift.