This study was conducted to examine die guinea pig as a suitable model for die study of the postburn hypermetabolic response and die febrile response that accompanies burn injury in man. Thirty animals were randomly assigned to four groups: >50% body surface area burn (n = 6); 45% to 50% body surface area burn (n = 10); <45% body surface area burn (n = 6); and controls (n = 8). On postburn days 3, 7, 11, 13, and 15, sequential temperature measurements were made. On postburn days 7 to 15, die randomly selected burn group (n = 12) and the control group (n = 8) had calorimetry studies performed. Sequential rectal temperature data demonstrate diat the guinea pig does not mount a prolonged or consistent febrile response after burn injury (p>0.05 for burn group vs control group on postburn days 7 to 13; p<0.05 for postburn days 3 and 15 only). However, the burned guinea pig is significantly hypermetabolic after burn injury, widi significant increases in dry and evaporative heat loss. The hypermetabolic response was proportional to burn wound size. Guinea pigs are not an ideal model for the study of die postburn febrile response; however, diis is an excellent model for the soidy of postburn hypermetabolism.