A case is made for the importance of measuring the accuracy of physicians' probabilistic diagnostic and prognostic judgments. Such measurement permits the recognition of deficient judgment. It also assists in the identification of physicians and technologies that can be used as sources of better assessments. Judgmental accuracy is not a monolithic, undifferentiated construct. Instead, there are several meaningfully distinct accuracy dimensions or components. This paper discusses probability judgment accuracy and analysis at the conceptual level, and also describes and illustrates how these concepts are operationalized in one particular class bf techniques.