We have named the sea surrounded by the Korean Peninsula, Primorye of Russia, and Japanese Islands as the East Sea. Historically this region has been variously named the East Sea, Chosun Sea, and, more recently, Japan Sea and Sea of Japan. Since the scientific research papers can play important roles on the naming the sea, the status of naming the East Sea in international scientific journals was investigated. Among 472 papers in 46 international journals that we assessed, Japan Sea (or Sea of Japan) was used in 322 papers (68.2%), East Sea was used in 21 papers (4.4%), and parallel usage of East Sea and Japan Sea accounted for 27.3% (129 papers). In all scientific papers before the early 1980s, East Sea was not used. Since the first parallel usage of East Sea and Japan Sea in 1985, these designations has been increasingly used. After 2004, the parallel usage has replaced the single designation of Japan Sea.