Leukemia-prone AKR mice were exposed twice a week to a 6 mT, 12 Hz or 460 Hz pulsed magnetic field for 30 min. If we take into account the five consecutive generations of mice, the above exposure actually took place in utero and, or during their life span. There was no difference in the incidence of leukemia or in the actuarial survival curves or in the average spleen or thymus weights.