Objevtives: To investigate the symptom prevalence and the primary intervention of work-related musculoskeletal diseases(WMSDs) and their related factors among manufacturing workers. Method: A self-administered questionnaire survey was conducted on 2,457 workers, at 22 enterprises in Chungnam province, Korea, from September 1 to December 1, 2003. The contents of the questionnaire included general and work-related characteristics, musculoskeletal symptoms and workers’past one-year experience of primary interventions. Results: 1. The overall symptom prevalence of the musculoskeletal diseases was 23.9%. The WMSD symptom prevalences at the neck/shoulder, arm/elbow, hand/wrist and back/leg were 14.8%. 2.7%. 7.3% and 12.0%, respectively. 2. In multivariate analysis, all WMSD symptom prevalences were high in the high workload, high force & high repetitiveness, and ‘high job strain’groups. The WMSD symptom prevalence at neck/shoulder was also high in females and the group experiencing low social support from the supervisor. 3. The rates of the primary interventions were as follows : 13.7% for health education, 5.8% for health counselling, 18.8% for preventive exercise, 24.7% for ergonomic intervention, and 9.8% for administrative intervention. 4. In multivariate analysis, the size of the enterprises and the type of occupational health management system(OHMS) were significantly associated with all primary interventions except health counselling(p<0.05). The other individual-level predictive factors were as follows. Those for the health education were male and union presence. Those for the health counselling were older age(≥40 years), irregular employment, and the active group of Karasek’s job strain model. Those for the preventive exercise were male, older age, longer tenure and regular employment. Those for the ergonomic intervention were longer tenure, job of physical force and/or repetitiveness, high job stain and the group experiencing high social support from the supervisor. The predictive factor for the administrative intervention was male (p<0.05). Conclusions: To establish an effective strategy for the primary prevention of WMSDs, approaches are needed which consider the individual nature of small and medium sized enterprises. Also necessary is to promote the participation of labor and management because the activation of the primary intervention was associated with the type of OHMS and union presence. Moreover the reduction of workload and increased intervention into the high risk group could be effective in the prevention of WMSDs.