Abstract: To investigate psychological effects of an ELF-EMF, an experiment with three conditions was designed. EMF field of 50 Hz and 1 mT accompanied by 45 dB SPL noise (EMF+Noise), Noise, and Control. Sixty-six subjects (Ss) participated the Control and one of the experimental conditions. Sequence of conditions (expositions) was balanced. Expositions were double-blind (except the obvious Control), lasted one hour and were separated by an one hour pause. During exposition Ss (three by three) performed tests on attention, perception, memory and filled out a psychological questionnaire. Statistical analysis (one-tailed probabilty) showed less attention (p <.05), perception (p < .05) and memory performance (p < .1) in Ss exposed to EMF+Noise compared to Control, whereas for Noise versus Control no difference was found. Comparing EMF+Noise versus Noise related to Control, reduced perception, less memory performance and more discomfort was observed (p < .1). Dividing Ss according to their selfrated sensitivity to EMF, all differences disappeared in the low sensitivity group (N = 30) and were pronounced in sensitive Ss (N = 36). Results indicate an immediate reduction of cognitive performance in attention, perception and memory performance by a 50 Hz EMF of 1 mT. These effects seem to be modulated by the selfperception of sensitivity to EMFs.