An accident model was used to analyze data in terms of the first event in all reported accidents occurring in a gearbox factory during 1974. The data were used to study the causes of lumbosacral injuries. A labor force of 2000 men sustained 99 lumbosacral injuries, 54 of which led to absence of one or more days. Twenty of the 54 were initiated by slipping, and 17 presented as a sudden onset of low-back pain without any preceding accidental event. A review of all patients who were absent following a slipping accident disclosed that the lumbosacral region was by far the commonest part of the body injured. Tripping was an infrequent cause of these injuries. Slipping rarely features in the literature as a cause of low-back pain. It is suggested that this is due to confusion between various contributory factors and events forming an accident.