This dissertation explores non-standard uses of German discourse particles, especially 'ja' (roughly: ‘as we know / uncontroversially’). After discussing arguments for the focus sensitivity of discourse particles, ample structural evidence in favor of this assumption is presented by natural instances of 'ja' in syntactically integrated and semantically embedded structures like restrictive relative and central, i.e. proposition-modifying, adverbial clauses. The acceptability of 'ja' in such environments and e.g. the nominal domain, i.e. mainly in adjectival phrases, depends, first, on the fulfillment of the felicity conditions of the particle. Second, it depends on information-structural properties of the syntactic complement of the discourse particle, which must contain or at least comprise a focus, or, more precisely, an element for which alternatives are evoked, even if the latter is not the primary focus of the containing sentence. My analysis of the information structure of complex sentences is based on a theory of discourse structure in terms of Questions under Discussion. This allows for an account of ordering alternations between discourse particles and clausal constituents, which sheds a new light on scrambling and comparable adverbial movement in German. I show that qualified claims on the grammatical requirements of discourse particles, particularly in non-root structures, cannot be made without due regard to the discourse context. I distinguish between unmarked uses of 'ja' and uses that are only acceptable in the right context, and infelicitous in isolation or the wrong context, but not unavailable, contrary to previous claims. Besides 'ja' and other exemplary German discourse particles, I consider comparable expressions in other languages and observe interaction with information structure as well as syntactic association with subsentential phrases. In German, debate of such small particle phrases is limited to focus and additive particles, and discourse particles in wh-phrases. I argue that ...