We developed a spreadsheet program based on Quattro-Pro version 2.0 to assist researchers, teachers, and practitioners to answer questions related to the development and application of diagnostic tests in epidemiologic studies and clinical veterinary medicine. Many results are presented graphically to facilitate interpretation. The five modules in the program are: test sensitivity and specificity; test agreement; comparison of test characteristics; relationships between test characteristics and disease prevalence; estimation of true prevalence based on test results. Examples from the veterinary literature are used to demonstrate output from the program.