Exposure to carcinogenic substances in the workplace creates an increased risk of certain types of cancer among employees. In The Netherlands, more than one million of the total working population of 10 million are exposed to toxic substances in more than 100,000 Dutch companies. To motivate workers to comply with protective recommendations, it is important to know their reasons for complying or not complying. The goal of the present study was to analyze the differences between workers who show a relatively high degree of protective behavior and those who show a relatively low degree of such behavior. The beliefs of workers exposed to carcinogenic substances at four worksites were analyzed. Data on attitudes, perceptions of social support, and self-efficacy expectations toward compliance with protective behavior were collected among 164 workers. The results showed that non-compliant workers perceived fewer benefits, encountered less social support, and, most importantly, encountered more barriers to complying with safety recommendations. It is concluded that health education programs must address these specific items to motivate non-compliant workers to comply more fully with protective recommendations.