AbstractThis paper reviews some of the issues related to the appropriateness of generalizing the results from clinical trials which have been conducted in genera] practice for smokers and excessive drinkers. We discuss the representativeness of the results related to the method of recruitment of general practices and patients to the study populations. We examine methodological issues and reasons associated with general practitioners’ and patients’ non‐compliance with maintaining the research protocols and intervention requirements which relate to the practice worthiness and the future uptake of interventions. When assessing the applicability of interventions to general practice, there are three basic research questions which should be looked at quite separately that relate to: efficacy, effectiveness and implement