Despite a large volume of research, understanding the influences on general practitioner referral behaviour remains limited. This paper argues for the value of an approach to this area based on the analysis of individual referral decisions, rather than aggregated referral statistics. A framework for analysing referral decisions is described, developed from a study that collected accounts of 167 referral decisions from 28 general practitioners. The framework enables referral decisions to be examined at three levels of analysis of increasing generality. It also encompasses factors that influence general practitioners against making a referral as well as those that influence them towards referral, as it was found that both types of influence can be discerned in most cases. The types of study in which the framework would be a useful analytical tool are discussed.