Ethanol sensitizes the nervous system of C. elegans to heat stress, which manifested in exacerbation of locomotion disturbances induced by exposure to constant temperature 36°C. Adaptation of C. elegans to high temperature by heat shock (1 h at 32°C and 1 h at 18°C) or two-hour exposure at 30°C resulted considerably reduced sensitivity of the nervous system to the negative effects of ethanol under conditions of heat stress.