The objective of the paper was to assess the microbiological condition of plums of ‘Węgierka’ variety that were osmotically dehydrated in sucrose solutions and, then, stored frozen during a period of 6 months. At 4-week intervals, in the fruit thawed in a vacuum-steam chamber, determined were total amounts of mesophilic and psychrophilic bacteria, as well as of fungi. It was found that along with extending the frozen storage time, the count of mesophilic and psychrophilic bacteria in the fruit samples analyzed decreased. The plums dehydrated in a 65 % sucrose solution for 1.5 and 3.0 hours had the least count of the microorganisms. In the fruit samples, which were not osmotically pre-treated (control sample) and which were stored frozen for half a year, the highest count of those bacteria was reported. It is also found that in the fruit dehydrated in the solutions showing a low concentration of sucrose, the amount of microbes was similar to that found in the conventionally frozen plums. The total quantity of mould and yeast in the material analyzed was reduced during their frozen storage. Regardless of the processing time, by the end of the period of frozen storage, no moulds were found in the fruit dehydrated in the solutions the concentration rate of which ranged from 55 to 65 %. The Bacillus genus bacteria were a prevailing micro-flora found in plums (about 75 % of the total count of bacteria). Amidst the identified moulds, the dominant types were Alternaria, Penicillium, Aspergillus, Rhizopus, Mucor, as well as Fusarium and Cladosporium.