β-oligosaccharides (OLS): β-galacto- and β-fructooligosaccharides are prebiotics. These substances stimulate the growth of beneficial to human health bacteria. In this article the characteristics of following oligosaccharides concentrates are presented: I-generation galacto-OLS (mixture after transformation of lactose), II-generation galacto-OLS (mixture after removing monosaccharides), lactulose concentrate and inulin concentrate. Analysis was dane by use of two HPLC columns (Aminex HPX 87 C, Lichrospher 100/NH₂) and under three different separation conditions. The HPLC profiles of analysed concentrates and the amounts of mono-, di- and oligosaccharides occuring in the concentrates are presented.