BACKGROUND: Low back pain has been estimated to be the most costly ailment of people of working age. Both work characteristics and individual factors have been identified as risk factors. The first interaction between work characteristics and individual factors occurs when workers start in their first job. AIMS: To investigate work-related risk factors for first-ever low back pain in young workers in their first employment. METHODS: A cross-sectional analysis was performed on 278 young workers in their first employment and without a history of low back pain prior to working. Work-related physical factors, psychosocial work characteristics, individual variables and first-ever low back pain were queried by means of a questionnaire. RESULTS: About half of the workers who developed low back pain after job start did so in the first year of employment. An increased risk was observed for (i) long periods of seated work [relative risk (RR) = 3.2, 95% confidence interval (CI) = 1.6-6.4]; (ii) more than 12 flexion or rotation movements of the trunk per hour (RR = 3.0, 95%CI = 1.4-6.4); and (iii) more than 3 years seniority in a job involving lifting more than 25 kg at least once an hour (RR = 3.7, 95%CI = 1.4-9.4). As to psychosocial work characteristics, first-ever low back pain was associated with a combination of low psychological job demands and low supervisor support. CONCLUSION: Work-related physical factors and psychosocial work characteristics should be considered as risk factors for first-ever low back pain. First-ever episodes of low back pain are common in the first year of employment. This may reflect a lack of work experience or training.