In studies on the metabolites of Pseudomonas, 3-chloro-4-(2-nitro-3-chlorophenyl)pyrrole and 2,3-dichloro-4-(2-nitrophenyl)pyrrole were found to exist, with oxypyrrolnitrin coexisting in the same cultural broth. The acetone extract of this bacterial cell was purified by column chromatography using silica gel and benzene-chloroform, and pale yellow rhombic crystals were obtained by recrystallization from ether-hexane solution. Structural analysis via mass spectrometry, elemental analysis, UV, IR, methylation, oxidation, and synthetic comparison revealed the structure of oxypyrrolnitrin (I) as 3-chloro-4-(2-nitro-3-chloro-6-hydroxyphenyl)pyrrole. Examination on the possibility of artificial formation of I from pyrrolnitrin showed such chemical oxidizing agents as oxygen and hydrogen peroxide to be useless for this transformation.