Previous tests of the phonological competition model (Dell, 1986) have mostly investigated the effects of phonological overlap (e.g. pick-pin) in isolated word production (e.g. primed picture naming). This is problematic since recent findings suggest that the effect of phonological overlap depends on the syntactic category of the phonologically related words, and few previous studies investigate phonological planning in the context of grammatical strings. We introduce a novel paradigm to examine two predictions of the so called parallel-then-sequential competition model (O‟Seaghdha and Marin, 2000) against data from the distribution of disfluencies in sentence production. We also extend previous work by comparing different forms of phonological overlap (identity vs. similarity) in both word onsets and rhymes.