This paper describes a method of preparating beta(1 --> 6)-linked galactofuranoside oligomers. The main structure of the acidic polysaccharide of Fusarium sp. M7-1 has a linear chain composed of beta(1 --> 6)-linked galactofuranose residues. For preparation of the beta(1 --> 6) galactofuranoside oligomers, glucuronic acid residues were converted to unsaturated sugars using an acidic polysaccharide lyase from Cellulomonas sp. Mild acid hydrolysis was found to be very effective in preparing the beta(1 --> 6) galactofuranoside oligomers from the unsaturated polysaccharide of Fusarium sp. M7-1. After treatment with 1M acetic acid at 100 degrees C for 5 h, the unsaturated polysaccharide was separated into oligomers, and the primary structures of the beta(1 --> 6) galactofuranoside oligomers were resolved, mainly by 400-MHz H-1-NMR spectrometry. These oligomers were resistant to commercial beta-D-galactosidases.