A study was performed at the Hartford Hospital to determine the value of routine screening electrocardiography in an outpatient population. Screening electrocardiograms were abnormal in 1,197 of 2,924 cases (40.9%). Dependence upon physician request or upon a positive response to a cardiovascular questionnaire resulted in the exclusion of almost one half of presumably unsuspected abnormalities. In a few clinics, the screening yield of abnormality approached the yield resulting from ECGs requested by physicians. In others, in the face of a virtual lack of requested ECGs, there was a significant frequency of screening abnormalities. Screening electrocardiography produced a yield of abnormality sufficient for it to be recommended as a regular hospital procedure. Interpretation of ECGs and compilation of statistical data were performed by automated methods, with the use of computer analysis.