This study was designed to examine the differences in the effect of an iron-deficient diet on iron metabolism in Fischer-344 (FC), Sprague-Dawley (SD) and Wistar (WT) rats based on hemoglobin (Hb), hematocrit (Hct), serum iron levels, growth rate and organ weight. Hb concentration was higher in FC rats (14 mg/100 mL) on the initial day than in SD (10) and WT (10) rats. Although the Hb level was significantly decreased in FC rats fed an iron-deficient (ID, 8 mg/kg) diet for 33 d compared to the FC rats fed an iron-adequate (IA, 50 mg/kg) diet, the relative concentration of Hb was high in FC rats fed the ID diet as compared to the SD and WT rats fed the same diet. A similar relationship was detected between Hct and serum iron concentrations. Although serum triglycerides (TG) were significantly increased in each rat strain fed the ID diet as compared to the IA diet, the percentage of the value for the IA diet was lowest in FC rats (119%) fed the ID diet as compared to the SD (328) and WT (394) rats fed the same diet. Retroperitoneal fat pad was decreased in FC, SD and WT rats fed the ID diet as compared to the IA diet. SD rats were particularly sensitive to the reduction of retroperitoneal fat pad. The results suggested that rat strains responded differently to dietary iron inadequacy, and that FC rats were less sensitive to an iron-deficient diet as compared to the SD and WT rats.