Cardiac murmurs have been recorded in patients in a number of clinical states which give rise to systolic cardiac murmurs, in which no abnormalities of the intracardiac pathway or direction of blood flow are known to exist: uncomplicated congenital heart block, chronic anemia, pregnancy, arteriovenous fistula, and hyperthyroidism. These recordings have been examined in the cathode-ray oscillograph and sound spectrograph. The oscillograms of murmurs of each of these groups have been found to be of the same general category, a basic wave of relatively low frequency (90-130 c.p.s.) with a variable amount of distortion by higher-frequency transient vibrations. The spectrograms of the murmurs of each of these groups have again been found to have the same general pattern: a relatively dense spectrogram limited to a fairly well-defined area, largely below the 250-c.p.s. level. Thus both the oscillograms and spectrograms of these murmurs showed the characteristics found in earlier studies of the innocent cardiac murmurs of childhood in contrast to the characteristics which have been found in murmurs of a number of lesions of rheumatic and congenital heart disease. Since the clinical states included in the present study have in common an increased stroke volume, this has been taken as supporting evidence of the thesis that the common innocent murmurs of childhood are caused by the vibration, at its natural period, of some structure in the cardiac wall or great vessels, arising from the ejection of an unusual volume of blood from the heart in systole or the greater velocity of ejected blood under these circumstances.