The Multi- and Single-Reader Sample Size Sample Size Program for Diagnostic Studies performs sample size computations for diagnostic reader-performance studies. Such studies are commonly used in radiology, where radiologists evaluate images resulting from an imaging modality (such as mammography for breast cancer) with respect to confidence of disease. In the most common study design, each reader reads all cases under each test. It is this initial study design that this first release (1.0) assumes. Other designs will be included in the near future. The program requires parameter estimates that are either conjectured or obtained from pilot data. Pilot data estimates can be obtained from analyses of data sets that use the method proposed by Obuchowski & Rockette and by Dorfman, Berbaum and Metz, and updated by Hillis and colleagues.