The purpose of this study was to discuss the implementation of nutritional education in public health services from the perspective of health professionals (physicians and nurses) working in them. The study was conducted in the Municipality of Campinas, São Paulo State, Brazil, from October 1993 to July 1995, using action-based research methodology. The results describe the construction of nutritional knowledge in training and professional institutions; behavior towards food-related problems in daily professional experience as compared to personal life; the contradiction between the apparently trivial act of eating and the complexity of dietary problems; the interface between the acceptance of this work and the incorporation of nutritional education activities and their actual institutionalization; and health professionals' opinions concerning situations permeating the implementation of activities. The paper concludes by referring to the need to implement nutritional education activities, difficulties experienced by physicians and nurses in approaching nutritional problems, and the importance of including nutrition in the curricula of health courses.