1. 1. The fatty acid composition of caribou (Rangifer tarandus) leg bone marrow decreased in saturation distally, which corresponds with changes observed in melting point. 2. 2. The major changes were in (a) oleic acid (C18-1) which increased from 42 per cent at the head of the femur and humerus to 74 per cent in the phalanges; (b) stearic acid (C18) which decreased from 21 per cent to 6 per cent; and (c) palmitic acid (C18) which decreased from 26 per cent to 13 per cent in the same tissue. © 1969.