Before and after conducting the health promotion program by group occupational health service during 5 years, we surveyed knowledge, attitude and practice about general health(30 items) and occupational health (30 items) among 25 small and medium scale industry workers (before : 355 workers, after : 279 workers) for evaluation of effectiveness. The scores of knowledge for smoking, drinking, cholesterol, mental stress, management of hypertension, and risks in younger or women workers were significantly increased after conducting group occupational health service. The scorers of attitude for controlling of fatty food consumption and cleaning workplace and bathing for health and that of practice for taking the periodic health examination and choking blood pressure were significantly increased but most of items in attitude and practice didn't be changed after services. According to sex, the scorers of men were significantly increased in knowledge of general health, but there were not significant differences in age, job status and work duration group. In conclusion, through the group occupational health service during 5 years, only the scores of knowledge in general health were increased. It suggested that the effective program which can change workers' attitude and practice for health promotion, should be developed and conducted in small and medium scale industry workers.