The aetiology of drug misuse is complex and multifactorial. Before developing educational programmes, it is important to understand the various psycho-social and environmental factors which contribute to health-related decision making. The Health Action Model provides an overview of these influences; it describes the interaction of knowledge, beliefs, values, attitudes, drives and normative pressures and seeks to show how these relate to individual intentions to act. It also indicates how environmental circumstances, information and personal skills may facilitate the translation of intentions into health actions. Finally, the relevance of the Health Action Model is considered for developing health promotion and health education programmes designed to reduce the onset of drug misuse.