Background: Accidental intrathecal vincristine (VCR) administration results in severe neurotoxicity, usually fatal in outcome. No specific therapy for initrathecal VCR toxicity has been reported so far. In our recent report, complete in vitro degradation of VCR by hypochlorous acid (HOCl) was demonstrated. Methods: In this comparative study, we examined the in vivo effectivity of HOCl in the cerebrospinal fluid of 24 New Zealand rabbits following intracisternal VCR administration. Results: There were no significant clinical or histopathologic abnormalities in the control and HOCl groups; however, multiple necrotic foci on histopathological examination of brain sections in the VCR group were determined. There were significantly lower numbers of necrotic foci in brain sections of rabbits which received HOCl administration than those without therapy. Conclusion: Our results indicate that HOCl may reduce VCR neurotoxicity. Copyright (C) 2000 S. Karger AG, Basel.