Abstract: This paper presents the late effects of accidental acute radiationinjury on humans, such as 1. The late effects of Hiroshima and Nagasaki atomic bomb survivors including 2800 uterine exposure cases. The epidemiologic studies that revealed the late effects with strong association, weak association and no associations. Fetus exposed to 1Gy during their 8^th-15^th pregnancy week, 43% of whom may have retardation in intellectual development which are over 50 times of risk factor more than those control group. Based on DS86 organ absorbed dose, the RR, EAR, and AR of cancers at different positions are given for atomic bomb survivors population. Offsprings who were born after their parents exposed to atomic bomb explosion were analysed by (1) untoward pregnancy out-come; (2)death incident; (3)frequency of abnormal children carrying abnormal sex chromosome etc genetic indicators, the average doubling dosage was estimated to be 1. 56 Sv which has evoked much controversy. 2. M edical effects of exposure of humans beings to fallout radiation from a thermonuclear explosion at Marshall islands with high frequency of thyroid diseases morbidity because of high radioactive iodine uptake in thyroid. 3. Medical effects of 23 Japan “Dragon boat” fishermen exposed to fallout radiation. 4. Late effects of American Y-12 plant radiation accident survivors, 4 of them developed radiation cataract and only 3 was alive in 1998. 5. Late effects of Chemobyl nuclear plant accident survivors in former Soviet Union : MDS were developed at 6 th and 9^th year later in two third degree ARS patients and also another one of 1^st degree ARS was diagnosed. M DS as well. At 11 ^th year after the accident, acute monoblastic leukemia was diagnosed in patient after ARS of 2 nd degree. 6. Late effects of Brazil ¹³⁷Cs accident.