The implication of NO in many inflammatory diseases has been well documented. We have previously reported that some chalcone derivatives can control the iNOS pathway in inflammatory processes. In the present study, we have assessed the NO-scavenging capacity of three chalcone derivatives (CH8, CH11, and CH12) in a competitive assay with HbO(2), a well-known physiologically relevant NO scavenger. Our data identify these chalcones as new NO scavengers. The estimated second-order rate constants (k(s)) for the reaction of the three derivatives with NO is in the same range as the value obtained for HbO(2), with CH11 exerting the greatest effect. These results suggest an additional action of these compounds on NO regulation.