Pectoral changes over the course of the sexual response cycle were examined using thermographic measurement. Three married couples volunteered to participate. Each couple reported to the thermography laboratory two times. Included within the two sessions (which were a minimum of a day apart) was a masturbation to orgasm sequence and a control behavior sequence. During both sequences, the thermographic image was focused on the pectoral region. An asymmetrical vasocongestive pattern was discovered in the right side of the pectoral region throughout the course of the sexual response cycle, for both men and women. The results were interpreted in terms of the structure and function of the lymphatics.