Water soluble proteins (WSP) in broad beans, Vicia faba, were purified, and their scavenging effects on free radicals and active oxygen species were investigated. The purification steps included ammonium sulfate precipitation followed by sequential chromatography on Sephadex G-75. The final gel filtration step yielded two peaks of scavenging activity, each containing M(r) values of 70 kDa (peak I) and 28 kDa (peak II). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of peak II fraction gave a single band with M(r) of 14 kDa, indicating that peak II protein is dimeric. WSP exhibited a marked scavenging effect on superoxide, and also an effect on hydrogen peroxide, but not so much on 1,1-diphenyl-2-picrylhydrazyl radical. WSP had only a small amount of sulfhydryl groups. Thus, the sulfhydryl groups are not responsible for the scavenging activity of WSP.