in water and wet soil. Dangers to man represent legionnaires present in artificial water systems, where baceria can persist in unfavorable conditions for up to a year. In warm and humid conditions, such as one present in various pool types (especially those with water temperature ranging from 20 °C to 45 °C), this bacterium can undisturbed survive and multiply for several months. The infection is resault of contact with contaminated water by aerosol inhalation or micro-aspiration. An increased risk of developing an epidemic occurs after a long not used period of the facility, and one of the examples of such practice is swimming pool with seasonal work regimen. The aim of this study was to show the microbiological quality of the pool in the area of the Primorje-Gorski Kotar County from the aspect of the presence of L. pneumophila. Data on the presence of this bacteria, as well as correlation with additional physico-chemical and microbiological basin water quality indicators, were analyzed in the four-year study period (2013 - 2016). The results indicate a generally low part (2%) of positive results of the L. pneumophila indicator, however, with the growth trend, that corresponding to the increase in spa pool part in the total number of analyzed samples. Generally, the number of all tested samples is growing, and is the largest in major tourist centers (Opatija, Krk, Rab). A higher part of positive samples occurs in fresh water. In positive samples, in regards to samples in which L. pneumophila was not shown, lower residual chlorine concentration and elevated UBB levels were observed, however the difference was not statistically significant. The T-test between positive and negative samples showed statistically significant difference only in the water temperature indicator, with significantly higher values in positive samples. Since the difference in the chlorine levels between the positive and negative samples is not statistically significant, the efficiency of the chlorine action on the legionnaires within the aquatic system is questionable. Namely, legionnaires can be proved at higher chlorine concentrations. After a more detailed analysis of the results of the four-year study, we conclude that in order to monitor the occurrence of L. pneumophila in water, the choice of the appropriate test method can be a crucial part of the study, and special attention should be paid to this. Also, in the future it is necessary to define the presence of L. pneumophila in drinking water from water supply systems, which is currently being carried out only in the case of epidemiological indications