1. 1. The fragile Saccharomyces cerevisiae mutant VY1160 has a cell-wall mannan with a lower molecular weight and a higher nitrogen content than the parental S288C strain. 2. 2. More mannobiose but less mannotriose and mannotetraose were found in O-glycosidically-bound oligosaccharides in the mutant. 3. 3. Acetolysis analysis of the alkali-stable mannan also showed a reduction of mannotetraose and an increase of the mannobiose fractions. 4. 4. Methylation analysis of total mannan, or side chains recovered after acetolysis, showed that in the mutant the amount of α(1-3)-linked mannose units prevailed over α(1-2)-linked residues. © 1983.