Job factors that affect risk of back pain were reviewed. Prevalence measures have been used to categorize the proportion of individuals with back pain. These measures include lifetime prevalence, period prevalence, and point prevalence according to the time frame. The frequency of back pain episodes is characterized by incidence ratio, incidence rate, and incidence density. Several studies that varied in methods, measures, and population have shown that jobs requiring very stressful manual load handling are associated with larger incidence rates of back pain than jobs with less stressful back load requirements. Four studies found that workers who must use most of their strength to perform the job were more likely to develop back problems than those who use less strength. Workers in jobs with high accident rates were found more likely to develop back problems. Traumatic events were found to contribute substantially to the incidence of work related back pain. Jobs that require nearly all standing or sitting postures were found to be associated with larger point prevalence of back pain. The increase could be attributed to other factors, such as vibration and impact, depending on the occupation. Pushing, pulling, carrying, asymmetric lifting and lowering, twisting, and bending have been implicated in back injuries. The author concludes that the following occupational factors are associated with increased incidence of back pain: general heavy work, frequent manual load handling, occasional very stressful load handling, load handling near one's strength capacity, accidents, and prolonged standing and sitting.