The concept of power loss through misclassification is well known. A simple method developed here yields a means for determing by how much power is lost. The method provides the basis for the development of an efficient screening methodology for the identification of high and low risk cohorts. This screening procedure is built on the well established retrospective cohort methodology and utilizes general records of mortality and morbidity for determination of the frequency of disease in the exposed and non-exposed cohorts. The size and power of the testing procedure compare favorably to that of a study with complete follow-up, while reducing the time and costs of study. This is particularly important in aiding epidemiologists in determining research and program priorities from among many areas of possible concern.