To assess the socio-economic impact of infectious intestinal disease (IID) on the health care sector, cases and their families, cases of IID ascertained from a population cohort component and those presenting to general practices were sent a socio-economic questionnaire 3 weeks after the acute episode. The impact of the illness was measured and the resources used were identified and costed. The duration, severity and costs of illness linked to viruses were less than those linked to bacteria. The average cost per case of IID presenting to the GP was £253 and the costs of those not seeing a GP were £34. The average cost per case was £606 for a case with salmonella, £315 for campylobacter, £164 for rotavirus and £176 for SRSV. The estimated cost of IID in England was £743m expressed in 1994/5 prices. The costs of IID are considerable and the duration of the illness was found to be longer than previous reports have suggested.