ALS genes of Candida albicans encode a family of cell-surface glycoproteins with a threedomain structure. Each Als protein has a relatively conserved N-terminal domain, a central domain consisting of a tandemly repeated motif, and a serine-threonine-rich C-terminal domain that is relatively variable across the family. The ALS family exhibits several types of variability that indicate the importance of considering strain and allelic differences when studying ALS genes and their encoded proteins. Analysis of ALS5 provided additional evidence of variability within the ALS family. Comparison of the ALS5 sequence from two strains indicated sequence differences larger than strain or allelic mismatches observed for other C. albicans genes. Screening a collection of commonly used C. albicans strains and clinical isolates indicated that ALS5 is not present in several of these strains, supporting the conclusion that the Als protein pro®le is variable among C. albicans isolates. Physical mapping of ALS5 showed that it is located close to ALS1 on chromosome 6. The Nterminal domain of Als5p was produced in Pichia pastoris to initiate structural analysis of this portion of the protein. The hydrophobic character of this portion of the protein was exploited in the puri®cation scheme. Circular dichroism analysis of the puri®ed, authenticated protein yielded a high content of antiparallel b-sheet and little to no ahelical structure. These results are consistent with the conclusion that the N-terminal domain of Als5p has an immunoglobulin fold structure similar to that found in many cell adhesion molecules. Gene sequences of C. albicans ALS5