This study was conducted to determine the factors affecting job satisfaction in workers by using the Job Stress Model proposed by the National Institute for Occupational Safety and Health (NIOSH). Data were collected from December 1 to December 30, 1999. The subjects were 2,133 workers employed at 155 work sites, who were examined using NIOSH Job Stress questionnaire translated by the Korea Occupational Safety ${\pounds}|$ Health Academy and Occupational Safety ${\pounds}|$ Health Research Institute. SAS/PC program was used for statistical analysis using descriptive analysis. Pearson's correlation coefficient, ANOVA, and Stepwise multiple regression analysis. The results of this study were as follows. 1. According to general characteristics of the subjects, job satisfaction was high in those with less number of children. 2. By work condition, job satisfaction was higher in those who were working in a permanent job position, were working with regular time basis than with shift basis, were working in regular shift hours than in changing shift hours, were working for a short period, and were working less hours and overtime works per week. 3. In terms of physical work environment, job satisfaction was significantly related to 10 physical environmental factors. In other words, job satisfaction was high in workers who were working in an environment with no noise, bright light, temperature adjusted to an appropriate level during summer and winter, humidity adjusted to an appropriate level. well ventilation, clean air, no exposure to hazardous substance during work hour, overall pleasant work environment and not crowded work space. 4. By work-related factors, job satisfaction was high in those with less ambiguity about future job and role, high job control/autonomy, and less workload. On the other hand, job satisfaction was low in those with little utilization of competencies, and much role conflict at work and workload. 5. As for the relationships between job satisfaction and the non-work related factors, job satisfaction was high in workers who were volunteering at different organizations or active in religious activities for 5-10 hours per week. 6. In the relationships between job satisfaction and buffering factors, significantly positive correlations were found between job satisfaction and factors such as support by direct superior, support by peers, and support by spouse, friend and family. 7. There were nine factors that affected job satisfaction in the workers: age, number of children, work hours per week, noise, temperature at the work site during summer, uncomfortable physical environment, role ambiguity, role conflict, ambiguity in job future, work load, no utilization of competencies and social support from direct supervisor. These nine factors accounted for 26% of the total variance in the multiple regression analysis. In conclusion. the following are proposed based on the results of this study. 1. The most important physical environmental factors affecting job satisfaction in workers were noise, role ambiguity, and work load, suggesting a need to develop strategies or programs to manage these factors at work sites. 2. A support system that could promote job satisfaction is needed by emphasizing the roles of occupational health nurses who may be stationed at work sites and manage the factors that could generate job stress. 3. Job satisfaction is one of the three acute responses to stress proposed in NIOSH job stress model (job satisfaction. physical discomfort and industrial accidents). Therefore, further studies need to be conducted on the other two issues.