Study Design. A questionnaire was given to 3,042 Japanese workers at a factory in 1992., It surveyed age, gender, weight, height, job classification, and work environment, as well as rile perceived causes, onset age, and characteristics of low back pain. Family history of low back pain among first-degree relatives and perception of physical condition also were assessed. Objectives. To investigate the risk indicators of low back pain in Japanese workers with various kinds of job classifications in a manufacturing company. Summary of Background Data. Risk indicators Of low back pain in Japanese patients have not been fully investigated in previous studies. Methods. Prevalence rates and characteristics of low back pain were examined among 3,042 factory workers (2,517 men and 525 women) with jobs with varying physical demands. In the analysis of risk indicators of low back pain, the odds ratios and 95% confidence intervals were computed, in addition, a multiple logistic analysis was performed to evaluate risk indicators of low back pain. Results. Point and lifetime prevalence of low back pain were correlated with the physical demands of the job. The perceived cause found to be most associate with low back pain were lifting in workers with jobs requiring moderate to heavy work and sports activity in sedentary workers. Family history of low back pain in parents, siblings, and children was a risk indicator of low back pain. The average age of the first attack of low back pain in workers with a family-history of it in their parents was significantly younger than that in workers with no family history. In a multiple logistic analysis in male workers, the physical work demands, age, and family history of low back pain in their parents were risk indicators; however, obesity was not a risk indicator. Physical and mental conditions of workers also were associated with low back pain.