Sialyloligosaccharides and sialylglycoconjugates in colostrum and milk are regarded to be important biological components with respect to be source of brain gangliosides in infant and to be antiinfectional components for the attack by the pathogenic bacteria and virus. Several acidic oligosaccharides have been characterised in both bovine and human milk or colostrum. The sialyloligosaccharide content of human colostrum and milk has been extensively studied, whereas that of cows milk and colostrum has received less attention. In this study, the concentrations of three sialyloligosaccharides of bovine colostrum and milk were determined at various stages during the prepartum and the first 7 d postpartum. The concentration of 3'SL (Neu5Ac(alpha2-3)Gal(beta1-4)Glc) reached a maximum value of 0.85 mg/ml immediately following parturition while the concentrations of 6'SL (Neu5Ac(alpha2-6)Gal(beta1-4)Glc) and 6'SLN (Neu5Ac(alpha2-6)Gal(beta1-4)GlcNAc) of 0.14 and 0.12 mg/ml, respectively, were much lower at this initial stage, although these concentration were maximum immediately following parturition. Bovine colostrum, especially that collected immediately after parturition, may be suitable as a source of 3'SL and other sialyloligosaccharides for use as additives by the food or pharmaceutical industries.