Low back pain patients and controls of shipyard workers were surveyed between June 1995 and September 1995 to identify risk factors of industrial low back pain. The patients were 17 male workers who had got medical treatment for over 3 days because of industrial back pain. Controls were 51 male workers who had not have musculoskeletal disorder for one year before the survey. By univariate analysis, the workers who did overtime work 4 times or more for the last 2 weeks showed odds ratio of 3.67 on low back pain with the workers who did less overtime work. Carrying heavy materials was also associated with the low back pain and the odds ratio increased with the increase of carrying weight. Work space and work posture were not associated with the low back pain significantly. The welder had higher odds ratio than the other workers on low back pain. The duration of employment and job satisfaction did not affect the risk of low back pain. Multiple logistic regression analysis showed that frequency of overtime work for the last 2 weeks and carrying heavy materials among the risk factors were associated significantly with the low back pain. We found that important risk factors of low back pain of shipyard workers are work intensity factors such as overtime work and carrying heavy weight.