Chaenomeles sinensis lectin (CSL) was isolated from Chinese quince fruit by affinity chromatography. The molecular weight of native CSL was estimated to be 16 kD by gel filtration chromatography. This lectin was found to contain approximately 57% carbohydrates. The molecular weight of deglycosylated CSL was estimated to be 3.6 kD by tricine-SIDS-PAGE under reduced conditions. Our results suggest that CSL may be a homodimer. The hemagglutinating activity of CSL was inhibited by N-acetyllactosamine and chicken ovalbumin, and it was drastically decreased at pH levels of 9.0 or greater. CSL may be a useful tool for the purification of glycoconjugates.