Fumaric acid-1,4-14C, L-aspartic acid-4-14C, and glycine-2-14C were supplied for 1 to 3 h to etiolated lupin shoots that were rapidly synthesizing asparagine. The distribution of 14C in aspartate and asparagine isolated from this material was determined. With aspartic acid-4-14C adminstration radioactivity was mostly in carbons 1 and 4 with carbon 4 having the greater amount; with fumaric acid 1,4-14C administration, radioactivity was again mostly in carbons 1 and 4. Aspartate labelled by fumarate contained relatively more radioactivity in carbons 2 and 3. Little radioactivity from glycine-2-14C entered either aspartate or asparagine and this was mainly in carbon 2 and 3. It is concluded that asparagine synthesis form aspartate is a major pathway of asparagine biosynthesis in lupins.