Exposure to noise can elicit generalized stress disturbances in the body by way of neuroendocrine mediation. The effect of exposure of a group of albino rats to noise produced by a full range loud speaker installed 50 cm directly above the animal cage producing a sine wave noise of 135 dB at 500 HZ for 3 hours daily for 7 days, was studied. Histopathological and electron microscopic (EM) examination of rat's cerebral cortex (temporal lobe), medulla oblongata and cerebellum and monoamine oxidase (MAO) and acetylcholinesterase (AChE) enzyme activity changes in the same brain parts were recorded. The results revealed non specific degenerative reactions to stress caused by noise in exposed rats and decreased enzyme activity of AChE and MAO in the medulla oblongata and temporal lobe respectively. These changes may explain the mental, neurobehavioral changes caused by noise stress.