CREENING of children for heart disease is at this time best done by an auscultatory technique. Previous articles have described the process of recording heart sounds on high fidelity equipment and listening to them on playback equipment (1-3). The main advantage of this process over direct auscultation is that the physician may listen to the tapes in a quiet place at a time of his, choice. A preliminary study to investigate the feasibility of this method for screening children's heart sounds for heart disease was begun in Chicago in 1954 (1). Satisfactory results led to a mass field trial on more than 33,000 school children in that city during 1959-60 (2,3). About 1,000 children were screened per week, using fixed equipment set up in a mobile trailer. Sixty-four cases of definite organic heart disease, a rate of 2 cases per 1,000 children screened, were found in the study. Half of these cases were previously unknown. In late 1961, the Advisory Committee of the Heart Disease Control Program, Chronic Diseases Division, Public Health Service, recommended that comparative and evaluative studies of this method be initiated using portable equipment assembled by the program from adaptable components available on the commercial market (4). Since the Pennsylvania Department of Health was interested in the method for possible use in school health programs, a preliminary field test using the ne-w equipment was conducted in that State during the 1962-63 school year. Lancaster County was selected as a trial area for several reasons. The Heart Association of Lancaster County, a new organization, was eager to initiate a community service project and the Pennsylvania Department of Health had a well-functioning cardiac clinic which could provide followup for the children found positive in screening. The county, a medium-sized community with 275,000 people, was ideal for a field trial. It had urban, suburban, and rural communities and schools. The study's main objectives were to: (a) test the practicability of using portable equipment by determining its portability and sturdiness and the frequency and cost of repairs and maintenance under field conditions; (b) determine how many children could be screened in an hour and in a school day; (c) ascertain the, number of tapes to which a physician could Dr. Myron M. Rubin, senior physician and associate cardiologist, Lancaster General Hospital, Lancaster, Pa., served for the Lancaster County Heart Association as medical administrator of the screening project described in this paper; Mrs. Bushnell served as project coordinator for the heart association. Dr. Hayman, associate director for preventive services, District of Columbia Department of Health, was at the time of the study medical director of region VI, Pennsylvania Department of Health. Dr. Levy is chief of the Congenital Heart Disease Section, Heart Disease Control Program, Division of Chronic Diseases, Public Health Service. The late Dr. William Kraus, director, division of chronic diseases, and Dr. Clarence A. Tinsman, chief, heart and metabolic diseases section, Pennsylvania Department of Health, were instrumental in obtaining support for this study, which was conducted under a contract from the Pennsylvania Department of Health.