Intentional and unintentional radiation exposures have a powerful impact on normal tissue function and can induce short-term and long-term injury to all cell systems. Radiation effects can lead to lifetime-defining health issues for a patient and can produce complications to all organ systems. Providers need to understand acute and late effects of radiation treatment and how the fingerprints of therapy can have an impact on health care in later life. This article reviews current knowledge concerning normal tissue tolerance with therapy.