One of the goals of antifungal therapy is to combine an anti-inflammatory activity with antimycotic properties, and therefore it is interesting to evaluate the capacity of active antifungal drugs to interfere with different phases of the inflammatory reaction. In order to identify a possible scavenger property of free radical species of the antifungal agent terbinafine, we studied its activity on the reduction of nitrotetrazolium blue chloride (NTB), induced by superoxide anions with the ultraviolet (UV)- and chemical-induced peroxidation of unsaturated lipid targets. NTB reduction was followed by spectrophotometer and the decomposition of squalene or methyl arachidonate by gas chromatography-mass spectrometry. Terbinafine (20 microgram and over) was capable of significantly inhibiting NTB reduction, indicating that the drug scavenges superoxide anion radicals. In these conditions no modifications of the concentration of the drug, as evaluated by high performance liquid chromatography, were observed. The UV- or chemically induced peroxidation of squalene and arachidonic acid was significantly reduced in the presence of 50 microgram of terbinafine, suggesting that the substance interferes with the chemical properties of peroxyl radicals. In all the tests used the degree of inhibition was proportional to the amount of free radicals generated. In conclusion our results indicate that terbinafine, at therapeutic concentrations, can be considered to be a free radical interceptor in vitro and could exert a mild anti-inflammatory activity in vivo.