Strain Monticello 2, a variant of Desulfovibrio desulfuricans, was isolated from an environment associated with Streptococcus allantoicus, which converts allantoin to oxamate. The strain grew with oxamate or oxalate, as well with more conventional substrates for Des. desulfuricans; yeast extract was essential for growth with oxamate, but not for growth with lactate. A cell-free extract formed oxalate quantitatively from oxamate but not from oxamide; it formed a hydroxamate in the presence of hydroxylamine. Unequivocal amidase or transferase activity towards acetamide was not observed. Frozen and thawed organisms decomposed oxalate but a soluble oxalic decarboxylase was not obtained; such preparations did not require ATP; they formed traces of formate from oxalate. The proposition that oxamate is an “incomplete substrate” of ecological value to this strain is discussed.