In eight normal subjects, ten patients with cyanotic congenital heart disease (group A) and seventeen patients with chronical pulmonary emphyema (group B) oxygen dissociation curves were determined by using the classical method of blood gas analysis according to Peters and Van Slyke. The curves were reproduced graphically. The mean curve of normal subjects corresponds well with the observations of other autors. Group A showed a significant rightward shift of the dissociation curve with a loose relationship to the present pH of arterial blood and the degree of rightward deviation. Group B showed a different course of the curves. In the state of complete cardial compensation the dissociation curve was partly displaced to the left, while in rightheart insufficiency a rightward displacement was observed. In some cases the curve was displaced to the left in the lower part, but to the right in the upper part. Factors which may be due to the displacement of the curves are discussed on the basis of literature.