Aims: The identification, differentiation and characterization of indigenous Saccharomyces sensu stricto strains isolated from Croatian vineyards and the evaluation of their oenological potential. Methods and Results: A total of 47 Saccharomyces sensu stricto strains were isolated from Chardonnay grapes and identified by physiological and molecular genetic methods. By using the standard physiological and biochemical tests, six isolates were identified as Saccharomyces cerevisiae and 41 as Saccharomyces paradoxus. However, PCR-RFLP analyses of the internal transcribed spacer (ITS1) region of the 18S ribosomal DNA identified 12 of the isolates as S. cerevisiae and 35 as S. paradoxus. Fermentation trials in a grape juice medium showed that these isolates ferment vigorously at 18°C and display tolerance to high levels of ethanol. None of these isolates appeared to produce either hydrogen sulphide or killer toxins. Conclusion: Saccharomyces paradoxus, possessing potentially important oenological characteristics, occurs in much higher numbers than S. cerevisiae in the indigenous population of Saccharomyces sensu stricto strains in Croatian vineyards. Significance and Impact of the Study: This study forms an essential step towards the preservation and exploitation of the hidden oenological potential of the untapped wealth of yeast biodiversity in the Croatian grape-growing regions. The results obtained demonstrate the value of using molecular genetic methods, such as PCR-RFLP analyses, in conjunction with the traditional taxonomic methods based on phenotypic characteristics in such ecotaxonomic surveys. The results also shed some light on the ecology and oenological potential of S. paradoxus, which is considered to be the natural parent species of the domesticated species of the Saccharomyces sensu stricto group.