The purpose of this article is to demonstrate that underspecification of lexical-entry forms enables us to restrict phonological theory to declarative statements about the structure of lexical items, and to avoid having recourse to feature-changing and deletion rules. The realizations of lexical items are mapped onto their underlying forms by means of filling-in, redundancy rules of two basic types, predictive and default. Predictive rules derive (at least) one feature from (at least) one other feature, given in the lexical entry form, and default rules provide a feature, if no other rule has applied. Rules are both universal and language-specific. Since all filling-in is accounted for by these redundancy rules, there is no need for a post-lexical component of the phonology.