In 1994, Eulalia speciosa (Poaceae) was found in a new locality in the southeastern Harima region, Hyogo Prefecture, western Japan. In this region, E. speciosa grows in Miscanthus-type dry grasslands formed on bald hills and on irrigation pond embankments. Phytosociological analysis revealed that these secondary grasslands were classified into one association and two communities. Eulalio speciosae-Miscanthetum sinensis, a newly recognized association peculiar to the southeastern Harima region, is characterized by the presence of a number of grassland species vulnerable in Japan, including E. speciosa, E. quadrinervis, Drosera peltata var. nipponica and Platycodon glandiflorum. The notable feature of the floristic composition of this association is a coexistence of tropical to subtropical Gramineous flora and cool-temperate herbaceous flora, both derived from regions in continental Asia with a relatively dry climate. Eulalio speciosae-Miscanthetum sinensis belongs to Arundinello-Miscanthion sinensis Suz.-Tok. et Abe 1959 ex Suganuma 1976, Miscanthetalia sinensis Miyawaki et Ohba 1970, Miscanthetea sinensis Miyawaki et Ohba 1970- Nearly all occurrencies of Eulalio-Miscanthetum sinensis are geologically restricted to areas with rhyolite pyroclastic rocks and lavas. The establishment of bald hills caused by fires and cutting, together with a dry climate and unique geology in the eastern Harima region, may be the main factors supporting the Eulalio speciosae-Miscanthetum sinensis in this region. Additionally, the existence of a large number of small grasslands on irrigation pond embankments seems to have provided suitable refugia for grassland species, through recent loss of grassland habitats caused by reforestation and progressive succession.