The authors observed temperature levels of saline and mannitol on the tips of bipolar diathermy forceps during application of power to the forceps and compared the effects of irrigation with saline and isotonic mannitol on electrical coagulation of vessels during neurosurgical operations. There was a marked rise in the temperature of saline corresponding to increased output power of the coagulator; there was no rise in the temperature of the mannitol. Irrigation with isotonic mannitol during surgery resulted in a considerable reduction of adherence of burned tissue and blood clots to forceps tips during coagulation of both arteries and veins compared with that which occurred during irrigation with saline. These results demonstrate that irrigation with an isotonic mannitol surpasses that with conventional ionic fluids, such as a saline, for prevention of both tissue adherence to bipolar diathermy forceps and removal of heat generated during electrical coagulation.