The purposes of the present studies were to clarify the effect of iron on the contents of the total free fatty acids, free unsaturated fatty acids, phospholipids, and unsaturated fatty acids in phospholipids in the liver, spleen, and muscle tissues of rats. Twenty rats were devided into 4 groups each consisting of 5 rats. A group was fed a control diet, B group was fed the same control diet and administered 3m1 of 1.5%Fe(OH)3 by intramuscular injection per week, C group was fed the control diet containing 2.5%Fe(OH)₃, and D group was fed the control diet supplemented with 5% of Fe(OH)3 for 60 days. The results obtained were summarized as follows: 1. Mean total free fatty acid concentrations is the liver, spleen and muscle tissues of A, B, C and D groups were 5.496, 5.570, 3.626㎎/g, 6.910, 5.938, 3.632㎎/g, 5.806, 5.076, 4.108㎎/g, and 7.462, 6.020, 4.330㎎/g, respectively. 2. Mean free unsaturated fatty acid concentrations in liver, spleen and muscle tissues of A, B, C and D groups were 2.202, 2,612, 1.860 ㎎/g, 2.676, 2.180, 1.936 ㎎/g, 2.418, 1.922, 1.894 ㎎/g, and 2.786, 1.950, 1.988 ㎎/g, respectively. 3. Mean phospholipid concentrations in liver, spleen and muscle tissues of A, B, C and D groups were 33.60, 30.56, 15.62 ㎎/g, 24.70, 29.32, 13.82 ㎎/g, 26.30, 29.16, 14.46 ㎎/g, and 24.54, 27.20, 13,24 ㎎/g, respectively. 4. Mean unsaturated fatty acid concentrations in phospholipids in liver, spleen and muscle tissues of A, B, C and D groups were 1.704, 1.364, 0.746 ㎎/g, 1.594, 1.316, 0.738 ㎎/g, 1.61, 1.32, 0.726 ㎎/g, and 1.188, 1.280, 0.648 ㎎/g, respectively.