Asparaginases catalyze the hydrolysis of asparagine to aspartic acid and ammonia. Enzymes with asparaginase activity play an important role both in the metabolism of all living organisms as well as in pharmacology. The main goal of this paper is to attempt a classification of all known enzymes with asparaginase activity, based on their amino acid sequences. Some possible phylogenetic consequences are also discussed using dendrograms and structural information derived from crystallographic studies.