In this article I show that weakening of unstressed vowels in Oscan, Umbrian and Paelignian occurs in different environments and at different points in the relative or absolute chronologies of the individual languages, and produces different results. Consequently, vowel weakening did not take place in Proto- or Common Sabellic as commonly thought, but should instead be seen as the longterm result of the generalisation of an initial stress accent across a number of languages in contact in Ancient Italy, including Latin, the Sabellic languages, and Etruscan.