Abstract Cell-free extracts from Pseudomonas fluorescens hydrolyzed L - and D -asparagine, L - and D -β-aspartohydroxamic acid and α-N-alkyl derivatives of DL -asparagine, but failed to attack L - and D -N-(β-aspartyl)-alkylamines. The extracts also catalyze the formation of β-aspartohydroxamic acid from L - or D -asparagine and hydroxylamine and the formation of α-N-alkyl-β-aspartohydroxamic acids from DL -α-N-alkyl derivatives of asparagine and hydroxylamine. The hydrolysis of D -asparagine, of D -β-aspartohydroxamic acid, of α-N-alkyl derivatives of DL -asparagine as well as the formation of hydroxamic acids from hydroxylamine and D -asparagine or α-N-alkyl derivatives of DL -asparagine were inhibited by α-amino acids. In the cases tested this inhibition proved to be competitive. Heating the extracts at 55° for 8 min caused a complete destruction of all the enzymic activities mentioned above. The presence during this heating of one of the substrates or of one of the amino acids that caused inhibition gave a complete or partial protection of all the above mentioned enzymic activities. The question whether the enzymic activities mentioned are catalyzed by one or more enzymes is discussed.