To determine if the endocrine response to microwave exposure was similar in a primate to that reported for other animals, rectal temperature and plasma levels of cortisol, thyroxine (T4), and growth hormone (GH) were measured in rhesus monkeys exposed to 1.29 GHz microwave radiation. Exposures were carried out under far-field conditions with the monkey restrained in a chair. Incident power densities of 0, 20, 28, and 38 mW/cm2 were used, with corresponding specific absorption rates of 0, 2.1, 3.0, and 4.1 W/kg. Blood samples were taken hourly via an indwelling jugular venous catheter over a 24-h period before, during, and after an 8-h exposure. Rectal temperature increased an average of 0.5, 0.7, and 1.7 degrees C for the three intensities used. No changes in T1 or GH were observed. Cortisol levels were increased during exposure to 38 mW/cm2. It was concluded that the temperature and adrenocortical responses to microwave exposure of the rhesus monkey are similar to the corresponding responses of other animals.