hen evaluating patients and making treatment decisions, physicians do not always have all the information necessary and may have to make judgments using limited information. This judgment is often intuitive in nature. The processes by which these judgments are made is of great theoretical and practical interest. In the 1960s, Amos Tversky and Daniel Kahnemann revolutionized the concept of human judgment. They introduced the notion that when individuals make judgments under uncertainty they use a limited number of cognitive processes. These processes are efficient and generally accurate, but can sometimes lead to errors or biases. In this review we discuss the nature of these processes and their potential effects on decision making.