This collective volume focuses on the crucial role of formal evidence in recognizing and explaining instances of grammaticalization. It addresses the hitherto neglected issue of system-internal factors steering grammaticalization and also revisits formal recognition criteria such as Lehmann and Hopper’s parameters of grammaticalization. The articles investigate developments of such phenomena as modal auxiliaries, attitudinal markers, V1-conditionals, nominalizers, and pronouns, using data from a wide range of languages and (in some cases) from diachronic corpora. In the process, they explore finer mechanisms of grammaticalization such as modification of coding means, structural and semantic analogy, changes in frequency and prosody, and shifts in collocational and grammatical distribution.