1. Halogen analogues of p-nitrobenzoate and benzoate were oxidized by washed cells of Nocardia erythropolis. 2. The oxidation of 2-fluoro-4-nitrobenzoate ceased at the level of acetate, and fluoroacetate was found in the incubation medium and particularly in hot-ethanolic extracts of the cells. 3. Several fluorine-containing intermediates were detected and 2-fluoroprotocatechuate was identified as one of them. 4. The nitro group was also reduced by the organism, as evidenced by the formation of 4-amino-2-fluorobenzoate. 5. Extracts of N. erythropolis activated fluoroacetate and condensed the resulting fluoroacetyl-CoA with oxaloacetate to form fluorocitrate. This product was a very powerful inhibitor of citrate metabolism by guinea-pig kidney homogenates and of the aconitase also present in the bacterial extracts. The inhibitions effected by synthetic fluorocitrate and the natural product were comparable. 6. 2-Fluoro-4-nitrobenzoate had negligible mammalian toxicity. 7. The isolation of fluoroacetate as a product of 2-fluoro-4-nitrobenzoate oxidation implies that the aromatic ring in this bacterium must be degraded via a gamma-carboxymuconolactone; fluoroacetate cannot arise by metabolism through the isomeric beta-carboxymuconolactone.