Introduction– Diarrhea is a two Greek word ‘dia’ and ‘rhein’ meaning ‘through’ and ‘to flow’ respectively. Hippocrates (460–370 B.C.) gave his clinical and epidemiological description of the entity of diarrhea.1 According to World Health Organization diarrhea is defined as having three or more loose or liquid stools per day, or as having more stools than is normal for that person. Acute diarrhea is defined as sudden change in consistency towards loose water stools > 3 times/ day in 24 hours. Acute diarrhea may persist for > 2weeks in 5–15% of cases, which is labeled as persistent diarrhea. It should not be confused with chronic diarrhea which is loose stools for > 14days, insidious in onset and associated with features of malabsorption. Rotavirus and diarrhoeagenic Ecoli are the most common pathogens responsible for acute diarrhea in children; Shigella, Salmonella, Campylobacter jejuni / Ecoli, Vibrio cholerae, Aeromonas, and Pseudomonas, occur more commonly in poorer areas and infections caused by protozoa and helminths occur mainly in areas where environmental sanitation is significantly deteriorated. Purpose of the study is to assess the serotype prevalence of different rotavirus diarrhoea in children under 5 years in hospitalized patient. Methods: A hospital based observational study was done with 400 patients to determine the prevalence of rotavirus infection along with epidemiology and their genotype in children below 5 years with acute Diarrhea. Four hundred children under 5 rotavirus positive(by IgM ELISA) children were selected for study . Background information, details of acute diarrhoea and treatment modalities were obtained from parents of the under 5 children. Any child having acute diarrhoea at the time of hospitalizations with rotavirus positive by IgM ELISA are taken for this study to find out prevalence of diferrent rotavirus serotype. This is a hospital based study conducted at a tertiary care hospital IMS & SUM HOSPITAL, Bhubaneswar the capital city of odisha, from 1stMay 2016 to 30st August 2018. Conclusion : Majority of the patients (43.8%) were in the age group of 12–23 months followed by 40.7% between 0–11 months, 10% between 24–35 months, 4% between 36–47 months and 1.5% betwwn 48–60 months. The mean age of patients was 15.40 ± 9.33 months.224 (56%) patients lived in nuclear family while 176 (44%) patients lived in joint family. Rotavirus infection was predominantly detected in the winter season (62.5%) followed by monsoon (25%) and summer (12.5%).Out of 400 samples, both G and P genotypes were identified in a total of 390 samples. In 2 samples, G genotype was determined while P genotype was untypeable. In 8 samples both G and P genotypes were untypeable.Among G genotypes, G3 was the most frequently detected (n=238, 59.5%), followed by G1 (n=104, 26%), G2 (n=16, 4%) and G9 (n=34, 8.5%). The predominant P genotype was P[8] (n=340, 85.4%) followed by P[4] (n=48, 12%) and P[6] (n=2, 0.5%). Four common G types (G1, G2, G3, and G9) and two common P types (P[8] and P[4]) accounted for 91% and 97% of the samples respectively.G3P[8] was the most common G/P combination found in 51% of the samples followed by G1P[8] (21%), G9P[4] (6.5%), G3G12P[8] (4.5%), G2P[4] (3.5%), G1G3P[8] (2.5%) and G9P[8] (2%).It was observed that G3P[8] genotype was significantly associated with duration of diarrhea and frequency of Stool over 24 hours (p<0.05)