This dissertation shows how signers mark polite register in JSL and uncovers a number of features salient to the linguistic encoding of politeness. My investigation of JSL politeness considers the relationship between Japanese sign and speech and how users of these languages adapt their communicative style based on the social context. This work examines: the Deaf Japanese community as minority language users and the concomitant effects on the development of JSL; politeness in JSL independently and in relation to spoken Japanese, along with the subsequent implications for characterizing polite Japanese communicative interaction; and the results of two studies that provide descriptions of the ways in which JSL users linguistically encode polite register. The studies show that JSL displays social indexical features with potential typological salience across sign languages.The elaborate system of overt encoding of polite expression in Japanese speech is commonly conceived of as indicating and reinforcing the special significance of polite behavior or practice in Japanese society. Nevertheless, sign language users as members of an overlapping society use a different language, which either marks politeness contrastively or fails to signify certain aspects of politeness signaled by spoken Japanese. The structural contrasts between JSL and spoken Japanese show that a language must receive consideration in light of actual communicative practice in order to determine its relation to social norms. Additionally, the reliance of JSL on dependent segments, or nonmanuals, to mark polite expression indicates that any linguistic analysis of politeness is impoverished as long as such kinds of dependent segments, analogous to features such as prosody in spoken languages, do not receive consideration.Since JSL and spoken Japanese represent, in a sense, two languages sharing one society, they represent a novel language contact context in which two languages segregate primarily via language modality rather than physical geography, as in the case of spoken contact languages. Using contact signed and spoken language pairs, researchers can uniquely tease apart the relation between language use and social context as a sign language is cultivated in a closely related society or ground of material relations of a preexisting spoken language.Chapter Two, "JSL as a Minority Language" illustrates the social context of Deaf Japanese people and JSL, and shows how Deaf Japanese inhabit a society dominated by a hearing culture. The resultant saturation in the language-context relations of the hearing culture produces a sign language with a number of influences from the socially dominant spoken and written language culture, along with concomitant effects on the JSL lexicon and morphology. A shared visual-kinesic communicative culture additionally results in a JSL that has assimilated features bearing resemblance to gestures from the inventory of speakers and signers. Chapter Three, "Japanese Signer and Speaker Polite Expression" demonstrates that although the structures of JSL and spoken Japanese differ, they have the capacity to index the same social interaction contexts. The presence of two differing languages, with a mixture of shared and unique indices, derived from a shared social milieu demonstrates that the examination of language structures in relation to their actual application is prerequisite to framing any cross-cultural analysis grounded in linguistic form. Chapter Four, "JSL Politeness Studies" unearths a number of JSL politeness marking features, including nonmanual, lexical and discourse features. The first study reproduces for JSL the Hill et al. Pen Study (1986) and elicits responses to a request for a pen signed with various levels of politeness. The second study replicates the Hoza ASL study (2007) and uses a Discourse Completion Test (Blum-Kulka et al. 1989) to collect responses from JSL signers to request scenarios. The close examination of polite expression via the two JSL studies shows that a subset of JSL politeness marking features appear to emerge from the visual-kinesthetic modality shared with Japanese speakers, as some features maintain enough transparency for non-signers to interpret them similarly to signers. Additionally, besides confirming some of the results of an earlier JSL politeness study by Okabe et al. (2005), the studies identify a number of politeness indices in JSL similar to register marking cues described in the ASL literature (Berkowitz 2008; Cokely and Baker-Shenk 1980; Hoza, 2007; Liddell and Johnson 1989[1985]; Roush 2007 [1999]; Zimmer 1989). JSL exhibits particular politeness indexing features shared with ASL, such as the polite grimace, manipulation of signing space size and variation of signing rate, which may have typological salience across sign languages.