Objectives: This study was carried out to examine the factors influencing the behavioral intention and behavior of workers with non-occupational diseases when utilizing medical facilities, using the theory of planned behavior (TPB). Methods: The first TPB questionnaire was administered to 3,116 subjects during workers’periodic health examinations at one health examination institute, between September and December in 2000. An investigation of the medical facilities utilization was also conducted by administering a second survey to the 354 subjects (11.4%) adjudged to be workers with non-occupational diseases from the results of the health examination. Results: The medical utilization rate within one month was 41.5%. To investigate the overall relationship between variables, the authors conducted a linear structural equation model analysis, based on the theory of planned behavior. The attitude toward behavior and the subjective norm both positively influenced the behavioral intention (T≥2.0). The perceived behavioral control and behavioral intention both positively influenced the behavior (T≥2.0) Conclusions: To improve the medical utilization by workers found to have diseases as a result of their health examination, the implementation of an intervention program will be necessary to increase the behavioral intention and perceived behavioral control, and care givers must pay more attention to eventually converting behavioral intention into actual behaviors.