This article presents a brief review of current mobile telecommunications systems, which represent a source of microwave pollution of the environment. It has been shown that the biological effects of radiation from cellular telephones involve the time factor for the real effects on the body. Results of studies of the biological effects of low-intensity modulated microwave irradiation, including that from cellular telephones, lead to the conclusion that irradiation does not have pathological effects on the body, but does induce the usual non-specific adaptive reactions. It is only in conditions of serious derangements of the immune system and prolonged exposure with cumulative effects that cancerogenic effects can occur in the body; as in other examples of external influences on the body, this is mediated by disruption of the balance between cellular repair systems and damage, the latter being favored. Several methods for studying low-intensity microwave irradiation are presented; these can be used for investigating its influence on psychophysiological functions in humans.