The aim of this study was to investigate the dynamics of the microflora during Montasio cheese ripening, with specific reference to some characteristics of biotechnological interest. Nine batches of Montasio cheese produced in different plants were analyzed. Streptococcus thermophilus was the predominant species throughout the whole ripening period of Montasio cheese. Enterococci were also frequently present. This microbial group resulted probably from milk, and its proportion decreased rapidly during ripening. The most acidifying microbial species was S. thermophilus, while the most proteolytic strains belonged to the genera Enterococcus. A high degree of phenotypic diversity occurred within the microbial species.