An ideal function test of the heart should correlate the clinical condition of the patient with the amount of work he can do, and the amount of effective work the heart can do. All too little attention has been given to a quantitative estimation of the work the patient can do and, when quantitative figures are obtained, the unmeasurable energy expended in maintaining the upright position is usually neglected. One of us (J. W. M.) has designed an ergometer that can be used while the patient is in the recumbent or semirecumbent position. This apparatus eliminates the waste of a rather large and variable amount of energy in maintaining posture, and is suitable for bedridden patients. By effective work of the heart is meant roughly, the mean blood pressure in grams per square centimeter times the output of the heart in cubic centimeters. In cases of regurgitation or stenosis, the