To estimate the merits of conformation therapy we made a treatment planning comparison and analyzed the quantitative dose advantage of conformation therapy over conventional treatment using a dose-volume histogram (DVH) of the critical organs. The DVHs of the critical organs were calculated and compared using the same average target dose. By using the Histogram Reduction Method, the equivalent dose to the full organ (ED) and the complication probability of the critical organs were both calculated. Assuming that the complication probabilities of each organ were independent, the entire complication probability was calculated by multiplying the uncomplicated probabilities of each organ and subtracting the product from 1. Dose response curves were then drawn and the TD₅₀'s and/ or TD₁₀'s of both techniques were determined and compared. The selected tumor sites were the brain, lung, bile duct, periaortic lymphnodes, cervix, prostate, and rectum. In every site, conformation therapy was advantageous over conventional treatment by 4 Gy to 41 Gy (6% to 82%) of the administered dose. The difference was much greater than that of the integral dose. Conformation therapy was especially promising in abdominal and pelvic tumors, but not in chest tumors because of the radiosensitivity of the lung. From this study we concluded that conformation therapy, theoretically at least, is promising. However, this advantage will have to be tested clinically in the future with dose escalation studies.