A Gram-positive, aerobic, non-motile bacterium was isolated from a decayed elm tree. Phylogenetic analysis based on 16S rDNA sequences revealed 99.0 % similarity to Cellulomonas humilata. Chemotaxonomic data that were determined for this isolate included cell-wall composition, fatty acid profiles and polar lipids; the results supported the placement of strain XIL11(T) in the genus Cellulomonas. The DNA G+C content was 73 mol%. The results of DNA-DNA hybridization with C. humilata ATCC 25174(T), in combination with chemotaxonomic and physiological data, demonstrated that isolate XIL11(T) should be classified as a novel Cellulomonas species. The name Cellulomonas xylanilytica sp. nov. is proposed, with strain XIL11(T) (=LMG 21723(T)=CECT 5729(T)) as the type strain.