Impingement of the rotator cuff beneath the coracoacromial arch without associated rupture of the cuff or reactive bone changes on the undersurface of the acromion is a well established clinical diagnosis. The value of subacromial bursography in the assessment of this condition was investigated in an anatomical study of fifteen cadavera and a clinical study of thirty-one patients. The subacromial bursa is situated like a cap over the rotator cuff and can be demonstrated roentgenographically by the injection of contrast material in shoulders from cadavera and living subjects. This bursa is composed of subacromial and subdeltoid portions as well as a subcoracoid extension in some individuals. However, it is the anterior portion of the bursa, under the coracoacromial arch, that is most significant, since this overlies the deep structures involved in the impingement syndrome. The normal subacromial bursa easily accepts five to ten milliliters of contrast medium. However, if the bursal walls are thickened and edematous, the bursa will be difficult to demonstrate roentgenographically or it will accept only a few milliliters of contrast material. The findings in this study suggest that when the findings on the bursogram are normal, a diagnosis of chronic impingement by the coracoacromial arch should be questioned.