Diarrhoeal diseases are a major problem in developing countries. Though precise data on childhood mortality associated with diarrhoeal diseases in Nepal are not available, it has been estimated that approximately 25 % of child deaths are associated with diarrhoeal disease, particularly acute diarrhoea. The purpose of this study was to assess the incidence of rotavirus causing acute diarrhoea in children less than 5 years of age. A total of 525 children with acute diarrhoea in a children's hospital of Kathmandu, Nepal, were enrolled between April and September 2011. The incidence of acute diarrhoea due to rotavirus was 25.9 % (136/525) as determined by ELISA. The percentage of rotavirus-infected males was higher (64.5 %) than females (35.5 %). The frequency of rotavirus cases was higher in children less than 2 years of age, among which the majority of cases (80.2 %) were in children between 6 and 24 months old (P<0.01). Genotypic characterization by RT-PCR revealed that the serotype G12 represented 55.9 % of cases in this study associated with P-types of either P[6], P[4] or P[8]. Further to this, a total of eight G/P combinations were identified, G12P[6] being the most common strain type of rotavirus in Nepal, with a prevalence rate of 46.4 %. The aim of this study was to find out the major genotypes of rotavirus causing acute diarrhoea in children.