OBJECTIVES: To estimate the health state utility of differing severities of gastro-enteritis associated with rotavirus infection in children under five. METHODS: Health state descriptions were developed based on the major symptoms of gastro-enteritis infection. Health states for children who could be treated at home and those requiring hospitalisation were presented to GPs (N=25), and for hospitalised cases, health states for children with two levels of dehydration were presented to paediatricians (N=25). Both GPs and paediatricians were asked to score these health states using the EQ-5D questionnaire for children in two age bands (<18 months, 1.5 - 5 years). Scores were modified to take into account the limited capacity for mobility and self-care among children in this age range. Utility estimates were calculated from these scores using standard methodology. RESULTS: From GP scores subjects requiring or not hospitalisation have a mean utility value (95% CI) of 0.425 (95 CI: 0.330; 0.520) and 0.781 (95 CI: 0.678; 0.884) in children <18 months, and 0.200 (95 CI: 0.049; 0.352) and 0.688 (95 CI: 0.553; 0.824) in children 1.5yrs - 5yrs respectively. From paediatrician scores, mean utility values for hospitalised cases with 3-8% and ³9% dehydration were 0.595 (95 CI: 0.528; 0.662) and 0.256 (95 CI: 0.157; 0.354) in children <18 months, and 0.634 (95 CI: 0.549; 0.718) and 0.077 (95 CI: -0.057; 0.210) in children 1.5yrs - 5yrs respectively. In each case, confidence intervals between severe and less severe health states did not overlap. CONCLUSION: Gastroenteritis associated with rotavirus has a significant impact on the health related quality of life in children under five. This study provides useful estimates of health state utilities for economic evaluation of interventions to prevent rotavirus infection.