On the basis of methylation analysis, 13C- and 1H-n.m.r. spectroscopic data, and the results of immunological methods, a new structure for the cell-wall alpha-D-mannan of the pathogenic yeast Candida krusei is proposed. In contrast to the alpha-D-mannans of other pathogenic yeasts of the Candida species, which have (1----6)-linked main chains and many (1----2)- and/or (1----3)-linked side chains, the C. krusei mannan is lightly branched and contains (1----2) and (1----6) linkages in the ratio 3:1.