[en] On the second mail survey (in 1984) concerning second cancers (leukemia and other cancers in the radiation field) following radiotherapy for malignant tumors, 108 cases were collected from 95 hospitals in Japan. Adding to 140 cases collected in the first mail survey in 1979, 248 cases were accumulated and analysed from a clinicopathological point of view. Underlying diseases (the first cancers irradiated) consisted of uterine cancer (106 cases), breast cancer (32 cases), laryngeal cancer (21 cases), malingant lymphoma (14 cases) and others (75 cases). One hundred and forty-seven cases (59 %) were classified as highly probable radiation-induced cancers (A-1 group) in which histological findings and organs of origin were clearly different from the initial cancers. Second cancers in A-1 group consisted of soft tissue sarcomas (39 cases), leukemia (23 cases), large bowel cancers (17 cases), skin cancers (10 cases), urinary bladder cancers (9 cases) and others (49 cases). Average latent periods were 5.7 years in leukemia and 15.0 years in the other solid tumors. In 9 cases of leukemia and in 10 cases of solid tumors, the latent periods were less than 5 years. On the basis of the population receiving radiotherapy for malignancies before 1977, which were collected in the first mail survey, incidence of radiation-induced cancers was estimated to be about 0.3 % of five-year survivors. (author)