<jats:title>Abstract</jats:title><jats:p>The structures of pyoverdin C, D, and E isolated from the culture medium of <jats:italic>Pseudomonas aeruginosa</jats:italic> (which are identical with the pyoverdins PaB, PaA, and Pa<jats:sup>6–8)</jats:sup>) have been elucidated by spectroscopic methods and degradation studies. The pyoverdins consist of a chromophore which could be identified as (1<jats:italic>S</jats:italic>)‐5‐amino‐2,3‐dihydro‐8,9‐dihydroxy‐1<jats:italic>H</jats:italic>‐pyrimido[1,2‐<jats:italic>a</jats:italic>]quinoline‐1‐carboxylic acid substituted at the amino group with a 4‐carboxy‐4‐oxobutanoyl (C), a 3‐carboxypropanoyl (D) or a succinamoyl residue (E) and at the carboxy group with the N‐terminus of <jats:sc>D</jats:sc>‐Ser‐<jats:sc>L</jats:sc>‐Arg‐<jats:sc>D</jats:sc>‐Ser‐<jats:sc>L</jats:sc>‐Orn(<jats:italic>N</jats:italic><jats:sup>5</jats:sup>‐OH‐<jats:italic>N</jats:italic><jats:sup>5</jats:sup>‐CHO)‐<jats:sc>L</jats:sc>‐Lys‐<jats:sc>L</jats:sc>‐Orn(<jats:italic>N</jats:italic><jats:sup>5</jats:sup>‐OH‐<jats:italic>N</jats:italic><jats:sup>5</jats:sup>‐CHO)‐<jats:sc>L</jats:sc>‐Thr‐<jats:sc>L</jats:sc>‐Thr]. In an appendix a tentative nomenclature for pyoverdin‐type compounds is proposed.