Amongst 440 strains of Pseudomonas stutzeri isolated from soil and marine sediment for a population genetic study, eight strains were each presumed to represent a novel genomic group and were compared with each other and to reference strains of P. stutzeri genomovars 1 to 10 and other Pseudomonas species by DNA–DNA hybridization, 16S rRNA and internally transcribed 16S–23S rRNA spacer region (ITS1) sequences and basic physiological properties defining the species. While 16S rRNA and ITS1 gene sequences positioned the eight strains within the phylogenetic branch of P. stutzeri, the DNA–DNA hybridizations with reference strains of the 10 described genomovars and among the novel strains were generally below 70 %, which is the threshold for species and genomovar differentiation. Since the physiological properties studied in the eight strains fitted the profile of P. stutzeri, eight new genomovars of P. stutzeri, numbered 11 to 18, are proposed, with strains 28a50, 28a39, 28a22, 28a3, 4C29, 24a13, 24a75 and MT-1 being the reference strains. The highly transformable reference strain 28a3 of genomovar 14 had a localized 16S rRNA gene sequence tag characteristic of genomovar strains 2 and 3, suggesting a possible horizontal gene transfer event involving part of the 16S rRNA gene.