A taxonomic study was made on the genus Tremex (Hymenoptera: Siricidae) in Korea. The study was carried out with specimens collected throughout the country from 1996 to 1998 and preserved in museums and laboratories of Universities in Korea and in other countries. As a result of this study, the genus Tremex found in Korea now consists of 5 species including one newly recorded species, Tremex contractus Maa and one new species, Tremex nigrocephalus n. sp.