PURPOSE: This study was conducted to determine factors affecting workers' physiological somatic complain using the Job Stress Model proposed by the National Institute for Occupational Safety and Health (NIOSH). METHOD: Data were collected from the 1st to the 30th of December 1999. The subjects were 2,123 workers employed at 155 work sites. Collected date were analyzed through SAS/PC program. RESULT: According to individual characteristics, younger and women groups showed significantly higher physiological somatic complaint than elder men groups. By work condition, groups with higher physiological somatic complaint included workers of irregular shift work. Dark lighting, improper temperature in winter, improper ventilation, inappropriate humidity, unpleasant work environment and crowded work place were significantly related with physiological somatic complaint. By work-related factor, physiological somatic complaint was high in those with higher variance in work load, quantitative work load, role conflict, job burden, role ambiguity and future ambiguity. On the other hand, physiological somatic complaint was low in those with little underutilization of ability. As for the relationships between physiological somatic complaint and non-work related factors, physiological somatic complaint was high in workers who had a side job, were bringing up infants alone, cleaned the house alone, cared for the elderly and disabled persons, were studying, were volunteering at another organization, and were spending 5-10 hours in religious activities per week. Physiological somatic complain was in significantly negative correlations with overall social support, supervisory support and family support, but in significantly positive correlations with co-worker support. CONCLUSION: The main predictors of physiological somatic complain were gender, shift work pattern, overtime work, ventilation, role ambiguity, role conflict, future ambiguity, job control, variance in work load, overall social support, worker with side job, worker who cleans the house alone, worker who is studying. These predictors explained 19.10% of the total variance of physiological somatic complain.