The 21-aminosteroids (lazaroids) are inhibitors of lipid membrane peroxidation and appear to function as oxygen free radical scavengers. The therapeutic potential of the lazaroid tirilazad mesylate has been extensively studied in several CNS disorders. Tirilazad and related compounds have been found to be highly beneficial in spinal cord trauma. Spinal cord injury studies utilising tirilazad are currently underway to determine the optimal combination of medications. Tirilazad has also been found to be beneficial in experimental head injury models, however current clinical studies have failed to confirm this efficacy, due in part to difficulties in obtaining therapeutic drug concentrations. Clinical studies using tirilazad in subarachnoid haemorrhage have been more promising. It has been shown to be beneficial in terms of reducing vasospasm and cerebral infarction associated with subarachnoid haemorrhage, and has now been approved in several European countries in this indication. Results from US studies are expected shortly. Finally, tirilazad has also been extensively tested in a variety of stroke models. Although it appears to be highly beneficial in experimental models, the clinical studies to date have failed to confirm this efficacy. Again, this failure appears to be due largely to inadequate drug concentrations having so far been tested.