F. tularensis is a gram negative cocobacillus 0.2-0.7 μm in size, asporogenic, immobile and does not possess fimbriae. The species Francisella tularensis comprises four subspecies (tularensis, holarctica, mediasiatica and novicida) of which Francisella tularensis subsp. tularensis (type A) is the most virulent and most pathogenic. It is causative agent of tularemia, a wildlife disease that can be transmitted to humans. The severity of the infection varies depending on the site of entry of the bacterium, the human immune status and the virulence of the agent. The aim of this study was to determine the viability of Francisella novicida in the water from lakes of Gorski Kotar. Lake Lokve, Lake Lepenica and Lake Bajer served as sources for sampling water for practical work. All three lakes were created artificially, that is, by constructing a dam that holds water in the appropriate area for the purpose of harnessing the water flow. In the practical work, the bacterial strain F. novicida U112 was used, while BCYE agar was used for cultivation. Other nutrient media were also applied in the study, depending on the bacterium of the permanent microflora of the water under study. Samples were processed by membrane filtration. Changes in F. novicida number in sterile and non-sterile samples were studied in the waters of Lake Lokve, Lepenica and Bayer for each lake individually. A comparison of all sterile water samples from all three lakes and all non-sterile water samples from all three lakes was also performed. Changes in the number of bacteria in the permanent microflora in the water samples of these lakes before and after the introduction of F. novicida were also monitored. Based on the results obtained, it was observed that F. novicida survives in the tested waters of Lokve, Lepenica and Bajer lakes and that it reproduces better in sterile and worse in non-sterile samples. Also, the introduction of F. novicida into specimens with natural microflora results in an increase in the number of other bacteria due to the fact that in the "competition" for nutrients they take up a greater proportion than F. novicida and thus prevent its growth and reproduction.