Traditional cautery, which is practiced widely in Saudi Arabia and some other countries, has not been exposed to detailed scientific investigation. In an attempt to elucidate some of its physiological aspects, we assessed the effect of cautery on a normal animal's nonspecific immune system. Male Wistar rats and guinea pigs were cauterized to simulate traditional cautery in size and percentage of cauterized area. Using radioactive sulfur colloid uptake and clearance, the effect of cautery on the mononuclear phagocyte system was evaluated in rats. The respiratory burst in peripheral polymorphonuclear leukocytes (PMNs) after cautery was measured in the guinea pigs using the chemiluminescence technique. The results showed marked reduction in the intravascular clearance of the colloid with prolonged clearance time following cautery. In addition, the liver uptake of the colloid was reduced in cauterized animals compared with control animals and the white cell count was also significantly reduced. The study showed marked inhibition of phagocytic function in guinea pigs in both whole blood and isolated PMNs. These results indicate that traditional cautery reduces the physiological function of the phagocytic system in normal experimental animals. The influence of traditional cautery on infected animals deserves further investigation.