This paper discusses the role of endogenous opioids in response to hyperthermia and the alterations observed in drug or alcohol addicts. Endorphins, rather than enkephalins are involved in adaptation to heat in the central nervous system. The pituitary secretion of beta endorphin together with ACTH in response to thermal stress provided the opportunity to measure the opioid reactivity to hyperthermia in health and toxicomania, as an index of opioid function, in adaptation to heat. The review of the data in the literature shows absent responses of beta endorphin and its related hormone ACTH to the thermal stress of sauna in heroin, cocaine or alcohol addicts. A common explanation for this phenomenon is that the long-term stimulation of hypothalamic opioid neurotransmission that is produced directly or indirectly by heroin, alcohol or cocaine, disrupts the opioid response to thermal stress, and thus the adaptation to heat.