The auxin activities of the homologs of racemic and enantiomeric α-alkylphenylacetic acids were estimated by pea straight growth test. The α-methyl, -ethyl and -propyl acids were moderately active whereas the longer and branched alkyl chain were found to make the molecule inactive. The more active enantiomers were shown to have the same con-figuration as the more active enantiomers in the other series of the optical active synthetic auxins.
