The present study was designed to investigate the lipid metabolism in bone marrow and peripheral blood cells. The author studied the in-vitro incorporation of (14)C-acetate Na into gross lipid fraction, major lipid fractions and fatty acids. Results were as follows. 1) The (14)C incorporation into the total lipid was markedly increased in bone marrow cells and whole blood cells of anemic rabbits. On the other hand, in Lanolin induced hyperlipemia, it was significantly decreased than in control, young or old. They were slightly increased but there were no differences among them. 2) After 4 hours' incubation of bone marrow or whole blood cells with (14)C-acetate in vitro, the percentage of the radioactivity recovered in diglyceride and free cholesterol was significantly increased in anemic rabbits, but in hyperlipemia decreased compared with control. 3) In hyperlipimia, the decrease of percent (14)C incorporation by bone marrow cells into fatty acid group 14:0+16:0 was supposed to be derived from the decreased activity of malonyl CoA pathway, while that into 20 Carbon and more longer chain fatty acid, formed via mitochondrial pathway, showed a significant relative increase. On the contrary, in young and old, especially in anemia, the increased activity of malonyl CoA pathway was observed in bone marrow cells but the decreased of mitochondrial pathway; the same result was obtained in peripheral whole blood cells, too.