Some of the new garments being developed for advanced fighter pilot's personal equipment will increasingly insulate the pilot, adding to the potential for discomfort and thermal stress. Two of these garments, 1) a counter pressure vest, and 2) a chemical and biological warfare suit, were investigated to determine their effect on pilot comfort. Both garments increase the number of layers of clothing worn by the pilot. This inhibits the transfer of heat, as well as the passage of water vapor, which reduces the cooling effect of perspiring.A combined physiological and cockpit model was used to determine pilot temperatures and perspiration rates. Flow velocities at the pilot were also considered in evaluating pilot comfort. In addition to traditional methods of air cooling the pilot, an advanced personal equipment cooling concept was investigated. The results show that the new garments insulate the pilot to such an extent that traditional air cooling is not adequate to maintain pilot comfort. However, the advanced personal equipment cooling concept is shown to provide adequate cooling without extremely high velocity air impinging on the pilot.