Cho, Yongjoon. 2017. “On the social indexicality of Korean plain-style interrogative markers -nya and -ni”. The Sociolinguistic Journal of Korea 25(3). 259~297. This paper investigates the sociolingustic variation of Korean plain-style interrogative markers -nya and -ni among the younger generation, from the viewpoint of indexicality. We adopted an experimental and a corpus-based analyses for this purpose. The experiment was a context-based acceptability judgement task with a 7-point Likert scale, and the corpus was collected from a synchronous computer-mediated communication, particularly from Kakao Talk, the most popular mobile instant messaging application in Korea. The experimental results show that women use -ni more than men, and the frequency of -nya forms increases when the addressee is male. The corpus results show that the females speak more politely to the females than to the males. We posit that the direct indexical meaning of -nya is ’intimacy’ and ’authoritativeness’, but -ni has the affective stance. In general, women are concerned abocut affective aspects of interaction. Because of these factors, -nya and -ni are gendered indirectly.