Different kinds of electromagnetic fields are treated regarding their possible effects on the human organism. Only scientific findings are taken as a basis for these considerations. According to the latest state of research only strong magnetic fields of low frequency and strong electromagnetic fields of high frequency can be critical for humans if exposed for a prolonged period. Possible causes for this threat are either the incidence of heart fibrillation or grave burnings of the body. Fields with such a strong intensity, however, are found only in few specific technical environments where they usually can be avoided by the specialists there. An impairment of well-being may also occur in connection with almost all other kinds of fields due to direct or indirect influence when the strength of the field becomes very high. An exception to that is only the static magnetic field where there are different findings from in-vivo- as well as in-vitro-experiments which, however, do not fit into these categories. Since the mechanisms of these effects are not understood yet, it is impossible to make statements about the medical relevance of the observed effects. Considering the variability and the partial inconsistency of the results found in magnetic fields it must be concluded that additional studies are necessary to validate these findings statistically. Last not least this also applies to the presumed and in public controversially discussed connection between the promotion of cancer and relatively weak time-varying magnetic fields, which in these low intensities occur not only in households, cars and trains, but also in almost all working environments.(ABSTRACT TRUNCATED AT 250 WORDS)