Purpose: Due to the continuously rising number of mobile phone users of an increasingly younger age, our preliminary study aims to assess the possible neurobiological effects of chronic exposure to microwaves possessing frequencies and power levels similar to GSM signals. For this purpose, rats were irradiated in their daily habitat. Materials and Methods: Twenty male Wistar rats (3 months old) were exposed to GSM 860–890 MHz for 4 hours a day for 36 weeks. This group was compared with sham-exposed rats. The medium exposure value of the microwave field power density was ≈60 mW/m2 and medium whole body SAR ≈ 0.15 W/kg. Two types of behavioral tests (open field test and elevated pulse maze) and a transmission electron microscopy on brain samples were performed after 3 and 9 months of exposure, respectively. Results: Exposed rats exhibited decreased locomotor activity and increased emotionality as compared with sham-exposed animals. Transmission electron microscopy examination, performed after 3 and 9 months of exposure, showed neurodegenerative alterations in the hippocampus and the frontal cortex. Severity of the alterations seems to be related to the duration of exposure. Conclusions: These preliminary results suggest that long-term and low-dose cumulative microwave radiation could cause, in rats, ultrastructural changes in neurons, glia and stress behaviour. Further research is needed to investigate the interaction between mobile phone radiations and the central nervous system at the molecular level.

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