The results of thermal applications to the abdomens of restrained, unanesthetized rats are reported. A silicone envelope through which water at 0. 10, 20, 30, 40, or 50°C circulated was applied while skin surface, subcutaneous, intraperitoneal, and colonic temperatures were measured. Pad applications at 0°C significantly lowered tissue temperature at all four locations measured. Pad applications at 10 and 20°C significantly lowered skin surface, subcutaneous, and intraperitoneal temperatures. Pad applications at 30°C significantly lowered skin surface and subcutaneous temperatures. Pad applications at 40 and 50°C significantly increased skin surface and subcutaneous temperatures, and applications at 50°C also increased intraperitoneal temperature. lntraperitoneal and colonic temperatures were insignificantly affected by pad applications of 30 and 40°C, and colonic temperatures were not significantly altered by any thermal application other than that at 0°C. The findings indicate that application of mild heat or cold (30–40°C) to the abdominal skin of the rat does not alter deep abdominal temperatures, indicating no deep vasomotor response to these thermal applications. The question can be raised whether these results suggest that a similar response may occur in humans.