The purpose of this study was to measure the effects of electromagnetic waves (EMW) at 900 MHz. EMW were produced by a signal generator and were administered to mice via an antenna. The frequency of the waves was tested by a spectrum analyser and a frequency-meter. The emitted power was 0.25 mW. A total of 117 mice (59 prepubertal and 58 adult) was used. Mice were exposed to EMW or sham radiation for 2 h and 20 h before an injection of pentylenetetrazole (PTZ). A statistically significant difference was found between the latency measurements within 20 h for prepubertal mice in stages 1 and 2 ( p<0.05). The effects on prepubertal mice of long-term 900 MHz EMW in a PTZ model may be an indication of possible problems in developing brains.