Coastal zone of the Republic of Croatia is especially sensitive and important resource, which is of the great public interest due to possibility of health risk. In this study the data were analysed from two sources. One source is the extended monitoring (2012. to 2014.), established with the goal of examining critical locations in the western part of the city of Rijeka (Kantrida) with 4-h sampling frequency. The other source of the data is the regular national monitoring of the seawater quality on the beaches, which has continuously been carried out since 1998. This study covers 5 locations: the 3. May (3M), Kantrida West (RW) and East (RE), Ploče West (PW) and East (PE). Microbiological examination includes two parameters (E. coli - EC and enterococci - EN) stipulated by Regulation (NN 73/08), as well as additional faecal (C. perfringens) and non-faecal parameters (S. aureus - SA i P. aeruginosa - PA). Some physical-chemical properties of seawater were monitored, like the water temperature, salinity, pH, turbidity, as well as environmental conditions (air temperature, rainfall, solar radiation). The aim of this study was to investigate the influence of environmental factors on time variations in values of microbiological parameters. Based on the results of the 17 seasons long examination it was analysed which of the investigated locations were the microbiologically most loaded. Additionally, the correlation analysis among the examined parameters was conducted. The results showed that microbiologically most loaded beaches are the 3. May, KE and KW, as well as that the peaks of the microbiological load on all beaches occurs in early morning (6 a.m.) and afternoon (6 p.m.) hours. Further analysis showed that solar radiation and salinity are important reductive factors of microbiological load. The amount of rainfall (72 hours before sampling) showed positive correlation with EC and EN, which are significantly negatively correlated with salinity and seawater temperature. SA and PA showed significant positive correlation with the number of bathers The causes of contamination can be related to the fact that nearby buildings are not appropriately connected to the drainage system of urban waste water as well as to the activity of the coastal freshwater springs.