Long-term musculoskeletal pain is a large public health problem with serious consequences for both the individual and society. Psychosocial factors have been shown to be good predictors of long-term disability and play an important role in the transition from acute to chronic pain. Early identification and intervention of those that run the risk of developing long-term disability would offer a great opportunity for reducing costs and personal suffering. The overall aim of this thesis was to assess a biopsychosocial approach to the assessment and management of musculoskeletal pain patients in primary health care. To this end, biopsychosocial assessment and treatment methods were tested in two different populations of primary care patients suffering pain. Results indicated that improvements in quality of life and work capacity one year after early multimodal rehabilitation were basically maintained after five years. The most salient prognostic factors determining return to work were educational level and the individual’s perceived health (Study I). Psychosocial factors as measured by the Örebro Musculoskeletal Pain Screening Questionnaire (ÖMPSQ) were related to disability and perceived health three years after treatment for non-acute pain problems (Study II). The experimental group in the controlled multimodal pain rehabilitation programme had lower health care utilization and a reduced risk of using large amounts of medication after three years compared with the participants in the control group. However, there were no significant differences between the groups on variables such as work capacity, function, catastrophizing and pain (Study III). Distinct profiles of catastrophizing, fear-avoidance beliefs, and distress were extracted and meaningfully related to future sick leave and dysfunction (Study IV). Our findings provide support for the biopsychosocial model and highlight the importance of psychosocial factors in long-term outcome. The results underscore the need for early identification of patients at risk. Further, multimodal treatment that covers not only biological but also psychosocial factors seems to be a key to successful treatment, and ideally this intervention should be matched to the patients' needs.