Japan was struck by a magnitude 9.0 earthquake and a tsunami on 11 March 2011. Although this catastrophe has caused the most devastating damage to Japan since World War II, we believe that our systematic preparation for disasters somewhat alleviated the damage. Learning lessons from the magnitude 7.3 Great Hanshin earthquake in 1995, the government organized approximately 700 medical teams specialized in disaster management. In this earthquake of 2011, hundreds of medical teams were successfully deployed and started operations within the first 72 hours. Furthermore, the internet, which was not commonly used in 1995, made significant contributions in communication among clinicians and enabled them to promptly identify the needs of the affected hospitals. In addition, medical professional societies took leadership in the logistics of transferring victims away from the disaster zone. We also observed that the spectrum of causes of death is distinct between the earthquakes of 1995 and 2011. In 1995, many victims died from trauma, including crash injury, and delays in providing hemodialysis contributed to additional deaths. In 2011, in contrast, many victims died from drowning in the tsunami, and most survivors did not have life-threatening injuries.