Objective

To investigate whether residence before and after birth near 50 Hz high voltage installations increases a child's risk of cancer and whether irk correlates with the strength of the magnetic field.

Design-A population based case-control study

Setting-Denmark.

Subjects-1707 children under tie age of 15 with leukaemia, tumour of the central nervous system, or malignant lymphoma diagnosed in 1968-86 and 4788 children taken from the central population register.

Main outcome measures-Proximity before and after birth to existing or former 50-400 kV electrical transmission connections and substations and associated historical electromagnetic fields calculated on the basis of current load on line, phase ordering of line, and distance from the dwelling.