Heat stress can be defined as build-up of body heat generated either internally by muscle use or externally by the environment. Heat stress induces severe hypothermia in highly productive organisms that are able to maintain their body temperature within a narrow range. This book presents research in the causes, treatment and prevention of heat stress. Topics discussed include heat stress in domestic fowl; molecular basis of heat stress damage in mammalian testis; breeding for heat stress tolerance in plants via molecular and physiological manipulation; heat induced impairments and recovery of photosynthetic machinery; caenorhabditis elegans as a convenient model organism for understanding heat stress effects; heat stress and extreme indoor environments and the impact of heat stress on blood pressure.