The activity of inducible nitric oxide synthase (iNOS) is increased as a response to several insults to central nervous system causing brain injury. To investigate iNOS expression in cadavers who died as result of traumatic brain injury (TBI), brain hemorrhage and brain congestion. Indirect immunohistochemistry was performed on 80 cases of brain injury (autopsies), as well 23 normal brain cases as a control group. The cases were stained for iNOS and interpreted in terms of staining intensity from 0 to indicate negative, 1 weak , 2 moderate and 3 to indicate strong staining reactions. Personal variables (age, sex, brain weight) were not associated significantly with brain injury type. The iNOS was not express in control group. But, strong activity of iNOS was expressed in neurons astrocytes and in cases of TBI and brain hemorrhage. The activity of iNOS in blood vessels was moderate. The rate of expression of iNOS in congestion cases was low in comparison with TBI and hemorrhage cases. The activity of iNOS was shown to be significantly correlated with TBI and hemorrhage. Strong reactions were localized within neurons and astrocytes. This possibly explains the mediated effects of iNOS on brain blood vessels in terms of blood vessels dilatation to accommodate with the severity of brain injury cases