Analysis of 492 electrocardiographic problems submitted by practicing physicians showed that interpretation often was hampered because of improper technique. Difficulties in recognition of the waves arose from artifacts, lack of clarity, shifting of the baseline, and improper standardization. Distortion of the curves resulted from improper stylus adjustment, placement of electrodes, labeling, or mounting. In some instances the full value of the electrocardiogram was not realized because the tracings were not taken at the proper time, the leads were too short, or insufficient clinical information was supplied. Most of the errors could have been avoided by proper preparation of the patient and machine and by inspecting the tracing as it was being recorded. The electrocardiographer must be constantly on guard to recognize such technical errors.