This book is the first detailed study since the 1970s of the characteristics of distinctive nasalization in sound change. Relying on copious cross-linguistic and experimental phonetic data, it evaluates the accuracy of universalist claims about nasalization phenomena, as well as the ability or otherwise of phonological formalism since the 1980s to describe sound change properly. It also examines the extent to which sound change is influenced by prosodic factors. Language data used in the study is drawn from around the world, with special focus given to historical developments in the Romance dialects of Northern Italy.