A Gram-positive, aerobic, motile, coccoid or short rod-shaped bacterium, 5420S-23(T), was isolated from an air sample collected in the Republic of Korea. According to phylogenetic analysis based on 16S rRNA gene sequences, strain 5420S-23(T) revealed 97.5, 97.3, 97.3 and 97.2 % similarity, respectively, to Cellulomonas biazotea DSM 20112(T), Cellulomonas cellasea DSM 20118(T), Cellulomonas fimi DSM 20113(T) and Cellulomonas chitinilytica X.bu-b(T). The peptidoglycan type of strain 5420S-23(T) was A4beta, containing l-ornithine-d-glutamic acid. The cell-wall sugars were galactose, glucose and xylose. The major fatty acids were anteiso-C(15 : 0) (49.7 %) and C(16 : 0) (20.0 %). The major menaquinone was MK-9(H(4)) and major polar lipids were diphosphatidylglycerol and phosphatidylglycerol. The DNA G+C content was 74 mol%. The results of DNA-DNA hybridization with strains of closely related Cellulomonas species, in combination with chemotaxonomic and physiological data, demonstrated that isolate 5420S-23(T) represents a novel Cellulomonas species, for which the name Cellulomonas aerilata sp. nov. is proposed, with strain 5420S-23(T) (=KACC 20692(T) =DSM 18649(T)) as the type strain.