Usually in Japanese, each NP in an argument position must be accompanied by an appropriate case-marker; however, in spontaneous spoken Japanese, the NPs often appear without case-markers (see e.g., Kuno, Susumu, 1973a. Nihon bunpoo kenkyuu. Taishukan Shoten, Tokyo; Kuno, Susumu, 1973b. The Structure of the Japanese Language. MIT Press, Cambridge, Mass.; Tsutsui, Michio, 1984. Particle Ellipsis in Japanese. PhD dissertation, University of Illinois; Masunaga, Kiyoko, 1987. Non-thematic Positions and Discourse Anaphora. PhD dissertation, Harvard University; Ono, Tsuyoshi, Thompson, S.A. and Suzuki, R., 2000. Discourse Studies 2, 55–84). This study particularly focuses on the deletion of the nominative case-marker ga from the perspective of information structure. The framework of information structure assumed here is not the binary frameworks such as ‘given/new’, or ‘discourse-old/discourse-new’ (see e.g., Chafe, Wallace, 1976. In: Li, C. (Ed.), Subject and Topic. Academic Press, New York, pp. 25–55, Prince, Ellen, 1981. In: Cole, P. (Ed.), Radical Pragmatics. Academic Press, New York, pp. 223–255; Prince, Ellen, 1992. In: Mann, W.C., Thompson, S.A. (Eds.), Discourse Description: Diverse Linguistic Analysis of a Fund-raising Text. John Benjamins, Amsterdam/Philadelphia, pp. 295–325), but the framework in which degrees of importance are recognized as a continuum (see e.g., Kuno, Susumo, 1982. Journal of Semantics 1, 120–154). It is demonstrated that the binary frameworks cannot distinguish the entire subject NP deletion from just the nominative case-marker deletion. The most relevant notion for the nominative case-marker deletion in Japanese is the notion of ‘Semiactive’ information proposed by Chafe (Chafe, Wallace, 1994. Discourse, Consciousness and Time: The Flow and Displacement of Conscious Experience in Speaking and Writing. Chicago University Press, Chicago). The generalization proposed in the present study is that when the information status of the subject NP is ‘Inactive’, no element can be deleted from the NP-ga; when it is ‘Semiactive’, ga can be deleted; and when it is predictable, hence ‘Active’, the entire subject NP-ga can be deleted.