The changes in total lipid, fatty acid, and lipid phosphorus contents were followed during germination and early growth of Rideau wheat seedlings at 24° for 72 h and 2° for 5 weeks. At both temperatures the changes in total lipids and total fatty acids were similar for seedlings at comparable stages of morphological development. In contrast, the phospholipid content of seedlings grown at 2° was considerably higher than that of seedlings grown at 24°. A marked increase in linolenic acid was also observed during growth at 2°, and this change occurred entirely in the embryo. The results indicate an increased synthesis and unsaturation of membranes in seedlings grown at 2°. The changes may contribute to the increased resistance to freezing temperatures exhibited by seedlings grown at 2°.