Abstract: The scavenging effects of cyprohepdadine (Cyp), an antiserotonin-antihistaminic agent with significant calcium channel blocker activity, on oxygen free radicals were studied. Cyp was found to significantly scavenge the hydroxyl radical (·OH) produced by Fenton reaction (Fe²⁺+ H₂O₂) (EC₅₀= 54μmol/L) and inhibit the rate of·OH generation (IC₅₀= 22μmol/L). The inhibitory effects of Cyp were significantly more potent than those of mannitol, a specific· OH scavenger, with EC₅₀ of 22.7 mmol/L and 10. 7 mmol/L respectively. Cyp was also shown to have certain scavenging effect on superoxide anion (O₂^-) produced by peritoneal polymorphonuclear leukocytes (PMNs) in rats (IC₅₀= 179 μmol/L). These results suggest that the anti-myocardial injury activity of Cyp may be, at least partially, related to its scavenging effects on oxygen free radicals.