The records of 3920 patients (2068 females, 1852 males) entering a model family practice unit between 1975-1978 were analyzed. Males [11%] and females [9.5%] reported an episode of low-back pain during the 3 yr interval. The complaint of medically reported low-back pain was significantly related to occupational factors such as: truck driving (P < 0.001), lifting, carrying, pulling, pushing and twisting (P < 0.001 for all variables), and nondriving vibrational exposure (P < 0.001). Patients reporting low-back pain reported more episodes of anxiety (P < 0.001) and depression (P < 0.001), and had more emotionally stressful occupations (P < 0.001). The mean number of pregnancies was greater in women with low-back pain (2.6) than in those without (1.6) (P < 0.001). The low-back pain sufferers were more likely cigarette smokers (P < 0.001), particularly when smoking was accompanied by a chronic cough (P < 0.001). This population is currently under prospective study to define the relevance of each of these risk factors to the complaint of low-back pain.