Psoriasis is a skin disease characterized by accelerated growth and loss of the normal maturation pattern of the epidermis. It represents a model to study the application of localized heating to a hyperproliferative but benign superficial skin disease. Thermal distributions in psoriatic plaques treated with ultrasound, water contact and infrared systems are presented. The concepts of Standard Thermal Dose and Equivalent Thermal Dose are introduced to quantify the total biological effect to tissue for a particular time and temperature during a hyperthermia treatment session.