||The main goal of the experiments described in this paper was to compare the behavior of Bulgarian words with vs. without «vowel/Ø» alternation. The Ø-form may for instance be observed, within the relevant word paradigms, in noun plurals, in adjectives’ gender and plural inflections, and in derived nouns. The materials in experiment 1 consisted of six sets of frequency controlled Bulgarian words, contrasting with respect to the following factors: Alternation (sets A1, B1, C1 with alternation vs. A2, B2, C2 without alternation), Morphology (set A with plural formation, an inflectional process, vs. set C with abstract noun formation, a derivational process), and Stress pattern (set A with first syllable stress vs. set B with second syllable stress). The experimental paradigm was based on repetition priming with visual-input lexical decision. Alternation had a clear effect on the lexical decision time, while Morphology (in the specific manifestation of this parameter) was virtually ineffective and Stress had a minor effect. The materials in experiment 2 consisted of two sets of adjectives contrasting with respect to Alternation (D1 vs. D2), presented in three forms: base-form, inflected (plural) and derived (the corresponding abstract noun). The results of experiment 2 substantially replicate those of experiment 1. The converging results of experiments 1 and 2 offer themselves to a relatively straightforward interpretation. The Bulgarian participants showed a sharp inclination towards full listing, i. e. direct access, of the morphologically modified forms (both inflected and derived) of morphophonologically complex, thus opaque, alternating words. By contrast, the morphologically modified forms of non-alternating, transparent words were clearly processed compositionally. As for the contrast inflection/derivation, although the specific instantiation of this opposition did not prove to directly yield a statistical difference, its interplay with the morphophonological complication implied by the process of vowel/Ø alternation produced a relatively clear effect in terms of lexical decision speed. Finally, the combination of vowel alternation and second syllable stress, involving replacement of the stressed vowel in morphologically modified forms, seemed to enhance the intimations of direct access.