The concept of causes is not just for professional philosophers to discuss. The epidemiologists also have to clarify how the concept is used since its meaning has profound implications for understanding basic measures of exposure-disease association. The concept of cause also has importance when designing a study or when analyzing epidemiological data. The paper describes the components cause model and its relationship with the mechanism of disease action. A measure of interaction is also presented which is based upon the components cause model. The common sense concept of causes also plays a fundamental role for the success of a health preventive programme according to the Health Belief Model. The component cause model may clarify causal patterns in situations when only a few of the exposed get the disease which the programme tends to prevent.