Changes in the levels of [(14)C]indole-3-acetic acid (IAA) and [(14)C]indole-acetylaspartic acid (IAAsp) were examined during adventitious root formation in mung bean (Vigna radiata [L.] R. Wilcz. ;Berken') stem cuttings. IAAsp was identified by GC-MS as the primary conjugate in IAA-treated cuttings. During root formation in IAA-treated cuttings, the level of [(14)C]IAAsp increased rapidly the first day and then declined; [(14)C]IAA was rapidly metabolized and not detected after 12 hours.