Two SDS-resistant endochitinases, designated as ASCHI53 and ASCHI61, were isolated from Aeromonas schubertii in a soil sample from southern Taiwan. MALDI-TOF mass measurement indicates the molecular weights of 53,527 for ASCHI53 and 61,202 for ASCHI61. N-terminal and internal amino acid sequences were obtained, and BLAST analysis of the sequences and MS/MS peptide sequencing showed that they were novel proteins. Degradation of chitin by these two endochitinases gave rise to hexameric chitin oligosaccharide, a compound known to have several potent biomedical functions. ASCHI53 and ASCHI61 retained, respectively, 65% and 75%, of their chitinase activity in the presence of 5% SDS and 100% of their activity in the presence of 10% beta-mercaptoethanol. These results demonstrate that they are SDS-resistant endochitinases and probably have a rigid structure.