This volume contains 22 revised papers originally presented at the 17th International Conference on Historical Linguistics, held August 2005 in Madison, Wisconsin, USA. The papers cover a broad range of languages, including well-studied languages of Europe but also Aramaic, Zoque and Uto-Aztecan, Japanese and Korean, Afrikaans, and the Pilbara languages of Australia. The theoretical approaches taken are equally diverse, often bringing together aspects of `formal' and `functional' theories in a single contribution. Many of the chapters provide fresh data, including several drawing on data from electronic corpora. Topics range from traditional comparative reconstruction to prosodic change and the role of processing in syntactic change.