The cause of acute lymphoblastic leukaemia is unclear and may be related to the environment and genetics.
It is thought that the cause of acute lymphoblastic leukaemia may be related to viral factors, ionising radiation, chemical factors and genetic factors. Ionising radiation has been shown to cause leukaemia in humans, and the incidence of leukaemia in areas exposed to severe radiation after the atomic bombings of Hiroshima and Nagasaki in Japan was 17-30 times higher than in areas not exposed to radiation.