Background: Diarrhea as an result of gastroenterocoltis kills 2195 children every day. Although the death rate has decreased in the last 15 years, it is still a major problem for the healthcare system. In undeveloped countries, the disease is transmitted due to lack od sanitary infrastructure, while in developed countries by insufficient disinfection in hospitals and with frequent travelling. Objectives: The aim of the research is to determine the frequency and distribution of bacterial and viral causes of enterocolitis, which were proven in the stool samples of patients at the University Hospital of Split in 2020. and to examine the susceptibility of the most common bacterial pathogens to antimicrobial drugs. Materials and methods: A retrospective perceptual study was performed to analize data collected from the archive of University Hospital of Split in 2020. All bacterial and viral causes of enterocolitis that were proven in the patients’s stool samples (except for recurrent strains in the samples of the same patient) were analyzed. Results: A total of 843 pathogens were detected. The most commonly detected pathogens are C. difficile (47 %), H. pylori (22 %), Campylobacter spp (11 %), Rotavirus (8 %) and Salmonella spp (5 Of the total number of detected pathogens, norovirus was 3 %, while EPEC and adenoviruses were represented by 2 %, and EHEC with only 1 %. The remaining 0.4 % of pathogens are C. upsaliensis, Aeromonas hydrophilia and Yersinia enterocolitica, each of which is represented by one isolate. Most isolates of C. jejuni and C. coli were well susceptible to macrolides (99 and 94 % of the tested isolates), but showed high resistance to quinolones (79 and 71 % of the tested isolates). Antimicrobal susceptibility testing for salmonella showed high susceptibility of isolates to trimethoprim-sulfametoxazole (100 %), chloramphenicol (98 %) and ciprofloxacin (77 %). Slightly lower susceptibility was to ampicillin (60 %) and amoxicillin/ clavulanic acid (65 %). Conclusions: The most common cause of diarrhea in the study period was C. difficile. The most commonly isolated bacterial pathogen is Campylobacter spp. Isolates of Campylobacter jejuni and Campylobacter coli have high resistance to quinolones. The most common viral cause of diarrhea is rotavirus. The frequency of individual causes of diarrhea varies with the age of the patients.