A survey was done on 1221 men between the ages of eighteen and fifty-five years who had been seen in a family-practice facility between 1975 and 1978 Each patient completed a questionnaire concerning any history of low-back pain, associated symptoms in the lower limbs, resultant disability, types of health care utilized, certain occupational characteristics, exposure to vehicular vibration, and sports activities. We found that 368 patients (30. 1 per cent) had never experienced low-back pain, 565 (46.3 per cent) had or were having moderate low-back pain, and 288 (23.6 percent) had or were having severe low-back pain. Patients with severe low-back pain had significantly more complaints in the lower limbs, sought more medical care and treatment for the low-back pain, and had lost more time from work for this reason. Risk factors associated with severe low-back pain included jobs requiring repetitive heavy lifting, the use of jackhammers or machine tools, and the operation of motor vehicles. Patients with severe pain were more likely to be cigarette-smokers and had a greater tobacco consumption as measured by both the number of cigarettes smoked per day and the number of years of exposure. Patients with moderate low-back pain were more often joggers and cross-country skiers when compared with the asymptomatic men and the men with severe low back pain. Otherwise, there were no identifiable differences related to sports activity.