Chelatobacter heintzii, which was described as a nitrilotriacetate-utilizing organism, was re-investigated in order to clarify its taxonomic position. On the basis of 16S rDNA sequence comparisons, it is obvious that this species clusters phylogenetically with species of the genus Aminobacter. The results of investigations of the fatty acid patterns, polar lipid profiles, polyamine patterns and quinone system supported this placement. The substrate-utilization profiles and fatty acid patterns of four strains (belonging to two different genomovars) revealed homogeneous results and showed high levels of similarity to Aminobacter aminovorans. DNA-DNA similarity studies confirmed that both genomovars of Chelatobacter heintzii belong to Aminobacter aminovorans. It could be shown that all species of this group are highly interrelated. On the basis of these data and previously published results, it is obvious that Chelatobacter heintzii is a later subjective synonym of Aminobacter aminovorans.