Genotyping and Severity of Rotavirus Infection among Infants and Children with Acute Diarrhea Introduction: Rotavirus (RV) belongs to the Reoviridae virus family and the virion comprises of three concentric protein layers. Worldwide, rotavirus (RV) is the most common cause of severe gastroenteritis (G.E.) among infants and young children especially in those countries which has not launched a RV vaccination program and approximately 40% of hospitalized patients suffering from gastroenteritis were infected with RV. Objective: To determine the prevalence of rotavirus infections, genotypes and degree of severity of its acute diarrhea in infants and children attending the children hospital, at Zagazig University Hospitals. Patients and methods: this study was done on 140 patients admitted to Children Hospital, Zagazig University suffering of gastroenteritis, Vesikari clinical severity score was done and stool sample was taken from patients, which was tested for RV by dipstick method and positive patients underwent genotyping by immunochromatography using PCR technique. Results: Among the studied group 128 patients (91.4%) showed positive results for rotavirus detection by dipstick analysis of stool, while only 12 patients (8.6%) were negative. The Vesikari score of severity ranged from 9 to 15 with median of 12 and its mean ± SD was 11.9±1.3. G3 and P8 were the most types in the examined patients. Conclusion: rotavirus is still the main cause of severe gastroenteritis that requires hospital admission. G3 and P8 are the most detectable genotypes.