Public health nursing is a synthesis of professional nursing and public health science. To assist people effectively to determine and enhance their health capabilities, it is essential that public health nurses have a sound understanding of the behaviors that improve or jeopardize health. This concern arises from the profession's increased emphasis on health behavior and from nursing's stated goal of health promotion. To examine the topic from the perspectives of public health and professional nursing, we examine several issues related to the concept and its definition. We hope that the discussion will stimulate analysis both to clarify the concept and to contribute to the development of public health nursing science.