A comparative correlational study was conducted to examine the knowledge and frequency of breast self-examination (BSE) by Greek health care professionals. A total of 268 women working in primary health care centers constituted the sample. The women were 22-64 years of age. Subjects reported low levels of knowledge about BSE and facts related to breast cancer. Multiple regression analysis showed significant relationships between level of knowledge and profession, number of years of health-related education, and frequency of BSE. The sample's frequency of practice of BSE was limited. Only 34.7% of the participants claimed to practice BSE on a monthly basis. Multiple regression analysis revealed statistically significant correlations between BSE behavior and marital status, professional experience with breast cancer, and level of knowledge. The level of knowledge of the participants is considered to be inadequate, taking into account that they work in settings where primary health care is offered. Courses of preventive medicine and health education should be incorporated in medical and nursing curricula.