Objectives-To describe workers with low back symptoms, to identify risk factors and to assess the occupational consequences separately in men and women. Methods-A descriptive study was conducted between 1 October 1996 and 31 December 1996 in a sample of workers selected at random from all types of small companies in the Paris area. A group of 202 occupational physicians interviewed 7129 workers with a standardised questionnaire including the Nordic questionnaire. Data analysis was performed by sex in the two groups: with low back pain and without low back pain over the previous 12 months. The group with low back pain was then divided into four subgroups: mild cases (without referred pain), moderate cases (with referred pain above the knee), serious cases (with referred pain below the knee), and low back pain with occupational consequences. Results-7010 questionnaires were able to be evaluated. The sample consisted of 54.8% of men (3842) and 45.2% of women (3168), with a mean age of 37.8 and 37.0 years, respectively (p<0.05). The following risk factors occurred significantly more often in men: high weight, height, body mass index (BMI), smoking, number of children, increased driving time and work time, material handling tasks, uncomfortable working positions. Most women were clerks (53%). Non-conditional logistic regression applied to the whole sample identified female sex as a risk factor (odds ratio (OR)=1.85, 95% confidence interval (95% CI) 1.58 to 2.13). The following risk factors were common to both sexes: lifting weights >10 kg, in women (OR 1.69, 95% CI 1.27 to 2.25) and in men (OR 1.27, 95% CI 1.06 to 1.53), uncomfortable working positions (OR 2.04, 95% CI 1.58 to 2.17 and OR 1.85, 95% CI 1.69 to 2.43), and absence of means to achieve good quality work (OR 1.39, 95% CI 1.19 to 1.63 and OR 1.38, 95% CI 1.15 to 1.65), respectively. Driving was a risk factor only in men and its importance increased with driving time (driving >4 hours a day (OR 1.61, 95% CI 1.24 to 2.09)). Severe low back pain was linked to female sex (10.2% of women v 6.6% of men), high BMI, aging, and uncomfortable working positions. Low back pain with occupational consequences (n=258) was not linked to sex, but only to aging and severity. Conclusions-The incidence and severity of low back pain were higher in women, although they seemed to be less exposed to known occupational risk factors. However, our results indicate a preponderance of these risk factors among female workers. Particular attention must therefore be paid to lifting of weights and uncomfortable working positions in female jobs (clerk, trading, health care staV). (Occup Environ Med 1999;56:696-701)