Soybean contains about 20% oil in seeds and it is therefore currently an important oil seed crop. Considering the fatty acid composition which constitutes the soybean lipid, the concentration of linolenic acid is less than 10%. On the other hand, wild soybean contains about twice the linolenic acid concentration and half as much lipid content as that of soybean. Based on these differences in the lipid content and linolenic acid concentration between soybean and wild soybean, a genetic study on the fatty acid concentration and lipid content using G. max × G. soja populations was carried out. These traits showed normal distribution and were highly heritable in F₂ and RIL populations; moreover; a negative correlation was shown between these traits. In addition, a QTL for the lipid content and linolenic acid concentration was detected in the same position near SSR marker Satt384 on LG E, suggesting that the factors controlling the lipid content might be partly shared by those of the linolenic acid concentration. Further elucidation of the regulatory aspects of these traits will provide information that could lead to the improvement of fatty acid composition and lipid content of soybean seeds.