While the use of radioactive materials around the world offers a wide range of benefits in medicine, industry and research, radiation accidents also occur in world-wide. The objective of this article is to provide useful information about radiation accidents to the medical personnel. For this, I attempted to document the circumstances leading to the accident and the subsequent medical treatment and health consequences of the victims. Radiation accidents described in this article are Chernobyl nuclear power plant accident, nuclear weapon accident in bikini atoll, major industrial accidents (Ir-192 Peruvian accident, Ir-192 internal contamination accident in Korea, Tokaimura accident in Japan) and Cs-137 contamination accident in Brazil. After reviewing major radiation accidents, I summarized the lessons to be learned from these accidents and presented the helpful institutes that can offer useful helps when radiation accident occurs.