Homoserine appears shortly after germination in pea seedlings and rapidly becomes the dominant soluble nitrogen component. It is synthesized only slowly from added 14C-glucose, and more rapidly from 14C-pyruvic and aspartic acids. Synthesis does not begin until the second day of germination, and increases thereafter. Homoserine is synthesized from added 14C-aspartic acid chiefly in the roots, and is translocated to the epicotyls. Added 14C-homoserine is converted rapidly into various alcohol-soluble and -insoluble components in the light, more slowly in darkness. Carbon from homoserine is widely distributed in the metabolism of epicotyls, and it is as effectively used as added aspartic acid. The results indicate that homoserine is involved in the mobilization and translocation of carbon and nitrogen reserves after germination in pea seedlings.