A bacterial strain, designated S9-5(T), was isolated from moraine samples collected from the north slope of Mount Everest at an altitude of 5500 m above sea level. A polyphasic study confirmed the affiliation of the strain with the genus Sphingomonas. Strain S9-5(T) was an aerobic, Gram-stain-negative, non-spore-forming, non-motile and rod-shaped bacterium that could grow at 10-40 degrees C, pH 5-8 and with 0-9% (w/v) NaCl. Q-10 was its predominant respiratory menaquinone. Diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, an unidentified phospholipid, an unidentified aminophospholipid and eight unidentified lipids comprised the polar lipids of strain S9-5(T). Its major fatty acids were summed feature 8 (C-18:1 omega 7c and/or C-18:1 omega 6c) and C-16:0. The G+C content was 65.75mol%. Phylogenetic analysis based on 16S rRNA sequences showed that strain S9-5(T) was phylogenetically closely related to Sphingomonas panaciterrae DCY91(T) (98.17%), Sphingomonas olei K-1-16(T) (98.11%) and Sphingomonas mucosissima DSM 17494(T) (97.39%). The average nucleotide identity values among strain S9-5(T) and Sphingomonas panaciterrae DCY91(T), Sphingomonas olei K-1-16(T) and Sphingomonas mucosissima DSM 17494(T) were 78.82, 78.87 and 78.29%, respectively. Based on the morphological, physiological and chemotaxonomic data, strain S9-5(T) (=JCM 34750(T)=GDMCC 1.2714(T)) should represent a novel species of the genus Sphingomonas, for which we propose the name Sphingomonas radio-durans sp. nov.