A decreased pO2 was found in the SHR rats' sensomotor area of the brain cortex in resting as well as in learning of the avoidance reflex as compared with the WKY rats. Avoidance training resulted in the decrease of pO2 in the brain tissue and the increase of common oxygen consumption. The recovery of common oxygen consumption to initial level took longer in the SHR rats. The number of the avoidance conditioned responses was greater in the SHR rats than in the WKY ones. The changes of the SHR rats' oxygen metabolism seem to be caused by morphological alterations, resulting in the peculiarities of the avoidance behaviour formation. These changes are enhanced in ageing and most obvious under emotional-motor loads in hypertensive animals.