The relationships among 12 oral yeast strains belonging to 5 yeast species were determined by one-dimensional electrophoresis of SDS-solubilized whole-cell proteins using different culture medium in the cultivation of the cells. The phenograms were made using Simple Matching coefficient (SM) and UPGMA clustering method. The strains investigated represented species from the genus Candida, species C. albicans, C. tropicalis, C. guilliermondii, C. parapsilosis, and C. krusei, all isolated from the oral cavity of normal and healthy people. The data obtained from the phenograms showed a high difference in protein patterns when all the species were compared using different culture media, suggesting that different. nutritional compositions led to the expression of different proteins derived from alternatives metabolic pathways expressed by the electrophoretic profiles. When looking to the different phenograms most species are not delineated as separate entities. A considerable protein electrophoretic heterogeneity is observed among strains of single species. From the data presented it seems that SDS-PAGE is characterizing at the strain level (unique profiles are obtained for each individual strain). Consequently, no taxonomic conclusions can be draw at the species level. Therefore the construction of a database of protein fingerprints is an important tool for the identification and characterization of these organisms.2917984