Molecular and Cellular Mechanisms.- Natural Environmental Radiation.- Accidents, Tests, and Incidents.- Medical Exposures and Workers.- Nuclear Workers.- Biased Epidemiological Studies.- Evidence Negating the Healthy Worker Eff ect.- Lung Cancer.- Breast Cancer.- Leukemia.- Liver, CNS, and Thyroid Cancers.- Lifespan, Birth Defects, and Experimental Cancer.- Animal and Human Cancer Therapeutic Studies.- Conclusions, Summary, and Importance.