An aldolase was partially purified from fermenter grownMycobacterium tuberculosis H37Rv cells. The aldolase has a molecular weight of 150,000, possesses a tetrameric structure and cleaves both fructose diphosphate and fructose-1-phosphate, the former being cleaved 17 times faster. The enzyme was inactivated by treatment with NaBH4 in the presence of fructose diphosphate or dihydroxyacetone, phosphate suggesting Schiff base formation during its catalytic function. Thiol reagents, EDTA and metal ions had no apparent effect on the aldolase activity. These results show that aldolase is of Class I type. However, this enzyme, unlike the mammalian Class I aldolase, was unaffected by carboxypeptidase A. N-ethylmaleiniide and dithionitrobenzoic acid.