The literature review concerning the mechanisms of biological effects in general and health effects in particular (excluding neoplasms), the effects occurring in the environment of weak electromagnetic fields (EMF) with power frequency of 50/60 Hz is presented. Based on this review, it can be stated that we are still far from understanding of the biophysic background of potential effects of EMF on human subjects. The well known mechanisms of interaction play an important role for power frequency electromagnetic fields with values considerably exceeding those occurring in the municipal environment and even those observed in the work environment. On the other hand, there is no sufficient experimental evidence that hypothetic interaction mechanisms of much weaker EMFs can be regarded as those with proven biological significance. Even if their occurrence is proven, an open question still remains whether biological effects resulting from the activity of power frequency electromagnetic fields generate adverse health effects. Epidemiological studies, carried out to date, mainly focus on carcinogenic effect of EMF, and pay less attention to possible risk of neurodegenerative diseases or cardiovascular and reproduction disorders. So far none of the above mentioned health effects has been adequately evidenced. It is most likely that some inadequacy in research methodology, and first of all diagnostic errors, uncertainties in exposure assessments or etiology of a given disease (the influence of other environmental factors on the studied health effects) are the major reasons for the present state of affairs. Therefore, further intensive studies are needed to eliminate the existing drawbacks.