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The transglycosylation activity of a novel alpha-glucosidase from the basidiomycetous yeast Xanthophyllomyces dendrorhous (formerly Phaffia rhodozyma) was studied using maltose as glucosyl donor. The enzyme synthesized oligosaccharides with alpha-(1-2), alpha-(1-4) and alpha-(1-6) bonds. Using 200 g/l maltose, the yield of oligosaccharides was 53.8 g/l, with prebiotic oligosaccharides containing at least one alpha-(1-6) linkage (panose, 6-O-alpha-glucosyl-maltotriose and 6-O-alpha-isomaltosyl-maltose) being the major products (47.1 g/l). The transglycosylatying yield was 3.6 times higher than the observed with the alpha-glucosidase from Saccharomyces cerevisiae (53.8 vs. 14.7 g/l). Moreover, when increasing the maltose concentration up to 525 g/l, the maximum production of tri- and tetrasaccharides reached 167.1 g/l, without altering the percentage of oligosaccharides in the mixture. Compared with other microbial alpha-glucosidases in which the main transglycosylation product is a disaccharide, the enzyme from X. dendrorhous yields a final product enriched in trisaccharides and tetrasaccharides.