Based on preliminary observations that continuous exposure to electromagnetic fields (EMFs) produced an after-effect on human brain electrical activity, the effect of 10 Hz, 1 gauss, on the intrinsic activity of the brain at that frequency was studied. Ten subjects were exposed for 10 min and the 10 Hz spectral power was measured during the 1 min interval following stimulation and compared with control values obtained from the same subjects. Significantly reduced brain electrical activity from the occipital electrodes following termination of the EMF exposure was observed, thereby confirming the preliminary results.