Background: Rotavirus is the most common cause of infectious gastroenteritis in children under 5 years with more than 140 million episodes per year. The aim of this study was to assess the severity of RV AGE in children under 5 years of age treated at the University Hospital for Infectious Diseases "Dr. Fran Mihaljević“, Clinical Hospital Centre Split and General Hospital Čakovec by using two measuring scales for the assessment of disease severity – Vesikari and Clark. Patients and methods: A total of 735 children with PCR detected RV AGE were included in this prospective multicentre study treated in three hospitals in Croatia (University Hospital for Infectious Diseases "Dr. Fran Mihaljević“, Clinical Hospital Centre Split and General Hospital Čakovec) from July 2012 until July 2014. Basic demographic and epidemiological data (date of birth, sex, age), as well as anamnestic details (number of watery stools, vomiting, body tempeature) were collected in order to evaluate disease severity (mild, moderately severe and severe RV AGE) by using the Vesikari and Clark scoring system. Results: According to Vesikari scale, the majority of patients 450 (61.2%) had severe RV AGE, while the Clark scale stratified the majority of patients into the group of moderately severe RV AGE. The distribution of patients into one of the three possible groups according to Vesikari and Clark scoring system was statistically significant (p < 0.00001). Conclusion: Vesikari and Clark scoring systems do not use entirely same criteria for evaluation of disease severity in patients with RV AGE. In addition, the scoring threshold for classification of patients into the group with severe RV AGE in Vesikar scale is lower (20/11 points) than that of Clark's scale (17/24). Therefore it is to no surprise that a significant difference in the distribution of patients into one of these categories (mild, moderately severe and severe RV AGE) has been established.