The present work was undertaken to study the changes in osmotic resistance of stored blood, used for blood transfusion. Blood samples of 50 cases from Orissa Red Cross Blood Bank, Cuttack, were studied. The blood was collected in acid citrate dextrose solution and stored at 4 degrees C. Storage was done under usual condition followed in blood banks. Osmotic fragility was determined at 3 days interval up to 15 days. In each case ESR was determined and in 20 cases plasma fibrinogen level was determined. In this study there was gradual increase in fragility which was maximum on 9th day and then slowly declined, which was statistically significant. ESR decreased markedly after 6th day, which was also statistically significant.