The species Arthrobacter viscosus was isolated from soil from Guatemala and it was classified into the genus Arthrobacter on the basis of phenotypic traits. Nevertheless, the results of16S rRNA gene analysis indicated that this species is a member of the genus Rhizobium, with Rhizobium alamii GBV016T and Rhizobium mesosinicum CCBAU 25010T as the most closely related species with 99.64 and 99.48 % similarity, respectively. The similarity values for the recA gene are 92.2 and 94.4 % with respect to R. alamii GBV016T and R. mesosinicum CCBAU 25010T, respectively, and those for the atpD gene are 92.9 and 98.7 %, respectively. Results of DNA-DNA hybridization analysis yield averages of 46 and 41 % relatedness with respect to the type strains of R. alamii and R. mesosinicum, respectively. Phenotypic characteristics also differed from those of the most closely related species of the genus Rhizobium. Therefore, based on the data obtained in this study, we propose to classify strain LMG 16473T as representing a novel species named Rhizobiumviscosum comb. nov. (type strain LMG 16473T=CECT 908T).