Transport and distribution of abscisic acid (ABA) and of naphthaleneacetic acid (NAA) within segments of Coleus petioles was studied. Transport of ABA is slow compared with that of NAA and is non-polar. Net loss of ABA from donor blocks is small and of the same magnitude as loss of mannitol from donors. Distribution inside tissue segments is identical for ABA and mannitol; the distribution of auxin is characteristic.