A novel actinomycete, strain PS33-18(T), that formed club-shaped and spherical structures borne on the tip of the aerial mycelia was isolated from a temperate peat swamp forest soil in Phu-Sang National Park, Phayao Province, Thailand. The isolate contained glutamic acid, alanine and meso-diaminopimelic acid in the cell-wall peptidoglycan. The whole-cell sugars of strain PS33-18(T) were glucose, madurose, mannose, rhamnose and ribose. The characteristic phospholipids were phosphatidylethanolamine, phosphatidylmethylethanolamine, hydroxy-phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol, phosphatidylinositol mannosides and ninhydrin-positive phosphoglycolipids. The predominant menaquinone was MK-9(H4). The major cellular fatty acids were C17:1�s8c, iso-C16:0 and C16:0. The G+C content of the genomic DNA of strain PS33-18(T) was 71.0 mol%. Phylogenetic analysis using 16S rRNA gene sequences revealed that strain PS33-18(T) should be classified in the genus Acrocarpospora. The level of similarity between this strain and the closely related species Acrocarpospora macrocephala NBRC 16266(T) was 98.3%, Acrocarpospora pleiomorpha NBRC 16267(T) was 97.9%, Acrocarpospora corrugata NBRC 13972(T) was 97.6%, Herbidospora sakaeratensis NBRC 102641(T) was 97.6% and Planotetraspora kaengkrachanensis NBRC 104272(T) was 97.3%. DNA-DNA hybridization results and physiological and biochemical properties indicated that strain PS33-18(T) could be distinguished readily from its closest phylogenetic relatives. On the basis of these phenotypic and genotypic data, this strain represents a novel species, for which the name Acrocarpospora phusangensis sp. nov. is proposed. The type strain is PS33-18(T) (=BCC 46906(T)=NBRC 108782(T)).