Fifteen non-fluorescent pseudomonad strains isolated from tomato pith necrosis (including 2 type strains), from northern, central and southern Portugal, Italy and Turkey, representative of each phenomenon obtained in a previous taxonomic study were analysed by randomly amplified polymorphic DNA (RAPD) analysis with a selected set of 19 Operon primers. Numerical analysis of the RAPD band patterns allowed the differentiation of two major groups corresponding to Pseudomonas corrugata and P. mediterranea isolates sharing approximately 50% similarity. At the 80% similarity level, four clusters Were distinguished. Cluster II, the largest one, consisted of six strains closely related to the P. corrugata type strain. Cluster III, included five strains closely related to the P. mediterranea type strain. Cluster I was represented by two strains that shared 65% similarity with cluster II, which contained the P. corrugata type strain. One unique strain that showed a slightly different banding pattern from the rest of the Pseudomonas strains was alone in Cluster IV. This strain was also atypical in the previous study. The 19 primers used in this RAPD study provided evidence for the great genetic heterogeneity within P. corrugata and A mediterranea species with the presence of divergent strains. This observation probably explains the difficulties of identification previously encountered: The taxonomic position and the divergent strains should be assessed by DNA-DNA hybridizations. Moreover, RAPD typing of non-fluorescent Pseudomonas spp. in tomato plants was shown to be a fast and accurate tool for epidemiological analysis of this pathogen.