This paper focuses on one aspect of a research study exploring the cognitive processes of decision making by 11 nurse practitioners and 11 general practitioners from the south east of England, using six patient scenarios during 2000. It sets out to explain some of their decision-making processes. This paper is part of a larger study discussing the use of information processing theory as a framework for exploring decision-making. Schema theory is used to provide explanation of correct and incorrect responses to the six scenarios. The paper explores areas in which cognitive overlap occurs and uses the participants’ examples to illustrate schema functioning. The usefulness of information processing theory to explore decision-making by nurse practitioners is also addressed. The paper concludes by suggesting that information processing theory and ‘think aloud’ approaches were suitable for identifying errors in decision-making, and could therefore be used as a teaching tool. Change is required in the culture of primary care organizations if shifting emphasis towards developing collective responsibility and greater openness is to be achieved.