The ability of a language's syntax to determine the application vs. non-application of postlexical phonological rules has by now been firmly established in a number of languages. Such rules, which apply above the word level, have come especially from the prosodic aspects of phonological structure, e.g. effects of syllabification, stress-accent, duration and tone. Much of the interest in this syntax-phonology interaction has centred around two general questions: (i) which specific properties of the syntax are available to affect the application of phonological rules?; (ii) how should these syntactic properties be incorporated into the phonology?

In some languages, vowels occurring in some specified domain, which is usually the word, must share some phonetic property or properties. Such languages are said to have vowel harmony.

Luganda, a Bantu language of Uganda, is unusual in having a vowel harmony system which is entirely morphologically conditioned. There is one subsystem which operates in the noun phrase and another irregular subsystem which operates in the verb phrase. The aim of this paper is to show how the non-linear theory of phonology developed by writers like Clements (1980, 1982) can throw some light on this apparently irregularity-ridden system.