In the study of languages such as Dutch, English, or Italian, unaccusativity and unergativity are two categories into which intransitive verbs may be classified, and which serve to explain various linguistic phenomena. According to many linguists, these notions can also be applied to Japanese. The aim of this paper is to review the historical background of the matter and the tests for unergativity and unaccusativity proposed in various studies, as well as to take an in-depth view at the direction of recent studies on unaccusativity and unergativity in Japanese.