Conformation radiotherapy is one of the best techniques for minimizing the radiation dose absorbed by the surrounding normal tissue while delivering a high dose to a cancerous target area. The cases of all patients who underwent external irradiation at Nagoya University Hospital from 1975 to 1992 were reviewed. A total of 5740 patients with 6179 lesions were irradiated during this time, and 3795 treatment plans involved radical intended irradiation. Of the 5740 patients, 1017 had head and neck cancer, 982 had cervical cancer, 506 had lung cancer, 439 had primary brain tumors, 308 had esophageal cancer, 1213 had metastatic tumors, and 1275 had other types of tumors. The total number of treatment plans per year decreased from 442 in 1975 to 292 in 1992. Likewise, the percentage of conformation radiotherapy performed in all patients decreased from 29.4% (130/442) in 1975 to 8.6% (25/292) in 1992. It occupied 14.5% (982/6179) of all intended plans, and 20% (775/3795) of radical treatment plans. The conformation technique was used in cases of cervical cancer (72%), esophageal cancer (65%) and primary brain tumors (25%). Boost Conformation radiotherapy represented 2% of all treatment planning and 29% of the conformation radiotherapy. Boost Conformation radiotherapy has recently become more popular and now represents more than 50% of conformation radiotherapy. With respect to cases of cervical cancer, the rates of local recurrence and late complications in cases treated by conformation radiotherapy were lower than in cases treated by two parallel opposed radiotherapy.