The hospitalization rates for gastrointestinal and respiratory illnesses in children under five years of age were examined on two Indian reserves in Northern Saskatchewan. The gastrointestinal illness rate was used as an index of waterborne disease, and the respiratory rate as an index of general health and of local customs affecting hospitalizations. The reserve rates were compared with those for other Saskatchewan status Indians and for other Saskatchewan residents. The risk ratios between the reserves and other Indians, and between the reserves and other Saskatchewan residents, were increased for both gastrointestinal and respiratory illnesses. The risk ratio of gastrointestinal rate divided by respiratory rate was greater for either reserve than for other Indians or other Saskatchewan residents. Waterborne illnesses were an even greater problem on the two study reserves than on other reserves. Comparing hospitalization rates for different illness groups is a useful method to compare the effect of different social factors.