In the present work the relative biological availability (RBA) of iron in the blood and the liver paste of swine has been studied by means of the hemoglobin regeneration technique in chickens. One day-old chickens were first made anemic on a low iron basal diet for 3 weeks, and were then divided into groups to which basal diets with various iron levels (10, 20, 40 ppm Fe) from different iron sources (ferrous sulfate reference standard, whole blood meal of swine and liver paste of swine) were subsequently fed respectively.After 16 days on test diets hemoglobin levels and hematocrit values in the blood of the chickens were measured. The chickens were then sacrificed for measurement of the iron concentration in their livers.Regression lines of each iron source were fitted by plotting final hemo- globin concentrations against the corresponding iron concentrations of the diet fed. Let the slope of the regression line from ferrous sulfate be 100, (i.e. relative bioavailability of ferrous sulfate), the RBA of the other 3 iron sources was as follows; processed whole blood meal of swine was 90.2; raw blood meal of swine 64.6; and the live paste of swine 78.4; but the differences between any two of them are statistically non-significant; i.e. their effects on hemoglobin regeneration are of the same extent.