The ultrastructural effects of gamma hydroxybutyrate after spinal cord injury were studied in rats. In the study 25 rats were divided into 3 groups. First group (group 1) consisted of 5 rats who underwent laminectomy only to serve as sham-operated group. Remaining 20 rats were randomly assigned to the control (group 2) or treatment (group 3) groups, consisting of 10 rats each. Animals were injured at C7-T1 by acute compression of the spinal cord with a clip exerting a pressure of 192 g. Gamma hydroxybutyrate treated and untreated rats were compared according to the ultrastructural and light microscopic findings. The main differences between the two groups were, 1) absence of vasoconstriction, 2) less edema, 3) absence of vessel wall necrosis, and 4) less myelin sheath degeneration in the gamma hydroxybutyrate treated group. The underlying mechanism is discussed. We have concluded that gamma hydroxybutyrate is an encouraging drug in experimental spinal cord injury in rats which need to be further investigated.