This study evaluated the cardiothoracic ratio (CTR) and the roentgenologic heart volume (RHV) as indexes of body fluid retention in 37 uremics on maintenance dialysis therapy. Both indexes related to a highly significant degree with the variations of body fluids balance assessed by the changes in body weights. Cardiomegaly (CTR greater than .500) subsided with adequate ultrafiltration therapy in most patients including those having blood pressure values within the normal range. It is concluded that the measurements of CTR provides an useful guide to ultrafiltration therapy especially in those patients whose blood pressure fails to sense the body fluid retention.