The. objective of this study was to investigate the effects of radiofrequency radiation emitted from cellular phones on: (1) trace elements such as manganese, iron, copper, zinc, (2) T1 relaxation times in serum, and (3) rectal temperature of rats. exposed to microwave radiation emitted. from cellular phones. Sixteen Sprague-Dawley rats were separated into two groups of eight, one sham-exposed (control) and one expo sed (experimental). The rats were confined in Plexiglas cages and a cellular phone was placed 0.5 cm under the cage. For the experimental group, cellular phones were activated 20 min per day, 7 days a week, for I month. For the control group, a cellular phone placed beneath the cage for 20 min a day was turned off. Rectal temperatures were measured weekly. For 250-mW-radiated powers, the whole body average specified absorption rate (SA R) (rms) is 0.52 W/ kg and 1-g-averaged peak SAR (rms) is 3.13 W/kg. The Mann-Whitney U test was used for statistical comparisons of groups. T1 relaxation time and the values of iron and copper in the serum of the experimental group were not changed compared to the control group (p > 0.05). However, manganese and zinc values in the serum of the experimental group were significantly different from the control group (p < 0.05). The difference in rectal temperature measured before and after exposure in the experimental groups was not statistically different from control (p > 0.05).