AbstractNa+, K+, and Ca2+concentrations in the blood serum and submaxillary salivary gland (SSG) were investigated in adult, male rats exposed to 2880‐MHz microwaves modulated with 1.5‐μs pulses at a pulse repetition rate of 1000 Hz or in a hyperthermal environment. Rats were exposed, one at a time, for 30 min to microwaves producing a specific absorption rate (SAR) of: 4.2, 6.3,6.8,8.4, 10.8, or 12.6 W/kg, or were sham exposed under similar environmental conditions. In a second series, one group of rats was exposed singly for 15, 30, or 60 min to microwaves producing an SAR of 9.5 W/kg and other rats were exposed for similar periods at 40 °C; and 10 rats were sham exposed. Flame photometric analysis indicated that the thresholds of microwave radiation required to induce a change in Na+, K+, and Ca2+concentrations in the salivary glands are 6.8, 6.8, and 6.3 W/kg, respectively. The directions of Na+, K+, and Ca2+ion shifts in exposed rats' salivary glands are similar, whether affected by microwaves or hyperthermia. Greater changes in Na+and K+concentrations in SSG of rats exposed to microwaves for 15 and 30 min were found than in those exposed at 40 °C. On the other hand, exposure to hyperthermia at 40 °C or to microwaves for 1 h caused Na+concentration to be increased by 68.7 and 59.5% and K+concentration to be decreased by 29.6 and 21.7%, respe