This document summarizes various thermal agents used in physical therapy including superficial heat, deep heat, moist heat packs, paraffin baths, infrared lamps, warm whirlpools, and contrast baths. It describes the physiological effects of superficial heat such as increased circulation, metabolism, and inflammation as well as decreased pain and muscle spasm. Precautions, indications, contraindications and set up procedures are provided for each modality.