ObjectiveTo determine what proportion of blood transfusions given in Mwanza Region, Tanzania could be avoided.MethodsA total of 1029 patients who received a blood transfusion in one of eight hospitals were analysed. Two sets of criteria for avoidable blood transfusions were determined, on the basis of a literature review.ResultsThe following percentages of blood transfusions in five groups of patients were found to be avoidable: operated patients, 8–24%; pregnant women, 8–10%; children aged under 5 years, 31–52%; children aged 5–14 years, 23–25%; and adults, 16–25%. Overall, 23–39% of blood transfusions were avoidable. At least 75% of all avoidable blood transfusions were to children aged under 5 years.ConclusionsThe largest reduction of blood transfusions can be achieved in children aged under 5 years, especially in infants aged less than 1 year. Following this study, blood transfusion prescribers drew up provisional guidelines on blood transfusions, which have been introduced in all hospitals in Mwanza Region. An evaluation study has been carried out and is being analysed.