The second World War (WWII) involved most of the world's nations and lasted from 1939-1945. Several countries were occupied during this period. One of these countries was Norway, which was occupied during a five year period from 1940 to 1945. Due to the rationing of several food items during the occupation period, the dietary habits changed. While the intake of fresh vegetables, fish and potatoes increased in people's diet, the intake of energy, fat, meat and milk consumption decreased. As a result of the occupation period, tobacco and alcohol was not easily accessible, thus the consumption of these items was also reduced. In addition physical activity changed for the Norwegian population during the occupation period. Assumptions that changes in these factors might have affected the risk of cancer for selective cancer sites during the occupation period are present. Thus we are interested in examining the impact of World War II on the cancer rates in Norway.