1. Based upon the intriguing report that nitric oxide synthase (NOS) inhibitor dose-dependently reverses N-methyl-D-aspartate (NMDA)-induced neurotoxicity observed in primary cortical cell cultures, many laboratories have investigated whether NOS inhibition is beneficial as a treatment for cerebral ischemia. 2. Although the results are variable, it is likely thought that nitric oxide plays a key role in pathomechanism underlying ischemic brain damage. 3. We review the experimental studies on effects of NOS inhibition on cerebral ischemia and measuring nitric oxide produced in the brain subjected to cerebral ischemia. 4. Finally, the possibility of NOS inhibitors as a therapeutical tool is discussed.