Little is known about the acquisition of decision-making skills in nursing students as a function of experience and academic ability. Knowing how experience and academic skills interact may help inform clinical education programs and formulate ways of assessing students' progress. The aims of the present study were to develop a problem-solving task capable of measuring clinical decision-making skills in novice nurses at different levels of domain-specific knowledge; and to establish the relative impact on decision-making of domain-specific knowledge and general ability as determinants of the acquisition of decision-making skills. Three types of clinical problems of increasing complexity were developed. Sixty second-year and third-year student nurses with high and low academic scores were studied in terms of their ability to generate hypotheses for a hypothetical case, recognize disconfirming information and the need to access additional information, and diagnostic accuracy. The results showed that general academic ability and knowledge function partly independently in the acquisition of expertise in nursing. Academic ability affects decision-making in low complexity tasks, but as case complexity increases, domain-specific knowledge and experience determines decision-making skills. There are important differences in the way novices with different levels of knowledge and ability make clinical decisions and these can be studied by systematically increasing the complexity of the decision task. These results have implications for the way in which clinical education is structured and evaluated.