Methodology for the objective and scientific evaluation of diagnostic systems has been greatly improved over the last 15 years. Many of the investigations that are now carried out on these systems include interpretation (reading) studies of normal and abnormal cases that are evaluated by receiver operating characteristics (ROC) analysis. In recent years, Picture Archiving and Communication Systems (PACS) for diagnostic radiology have begun to be developed by a number of companies which hold the belief that in the near future much more of radiology's traditional work will be done electronically. Unfortunately, many of the basic questions about the clinical relevance of these undertakings have not been addressed in adequate detail. The application of ROC analysis to the problems involved in the development and operation of the PACS systems clearly would help answer a number of these questions. It is the purpose of this program projects to address some of these important issues through a series of multiple observer studies in which we will evaluate the requirements of diagnostic systems as related to picture archiving and communications. We expect these investigations to yield specific recommendations for display requirements of PACS in the radiology environment.