Assessment of community knowledge and practices relative to a given health problem is a critical but often neglected first step in the development of health education and health personnel training programmes. Quantitative surveys on knowledge, attitudes and practices (KAP) are inadequate in terms of understanding underlying socio-cultural variables which programmes should take into account. Qualitative anthropological methods have been found to be more appropriate in terms of providing insights for the development of culturally relevant programmes. The semi-structured group interview is one qualitative method which is increasingly being used in pre-programme assessments. This paper reports on the use of the group interview method in a study of community perceptions and treatment of diarrhoeal disease in the Tunisian Diarrhoeal Disease Control Project. The steps involved in planning and implementing a study using this qualitative methodology are discussed. Examples of policy recommendations for health education and health worker training based upon study findings are presented.