Pseudomonas spp. of the fluorescent group produce siderophores (so-called pyoverdins) consisting of a peptide chain attached to a pyrimidoquinoline ring system which is derived from a condensation product of L-Dab and D-Tyr. Commonly several related compounds are found to accompany the pyoverdins having the same peptide chain, but differing in the heterocyclic part. The structure elucidation of a new variety (succinopyoverdin) is described here.