Theories of lexical access in speaking differ in whether they assume that words are accessed in a conceptually decomposed or non-decomposed way. In this paper, two experiments are reported that test the non-decompositional theory and computer model proposed by Roelofs (1992a). Subjects had to name pictured actions using verbs and ignore distractor verbs superimposed on the pictures. According to the theory, semantic inhibition should be obtained from distractor cohyponym verbs that are the names of other pictures in the experiment. By contrast, semantic facilitation should be obtained from hyponyms of the target verbs. Both predictions were empirically confirmed, both qualitatively and quantitatively. These findings support the proposed non-decompositional theory and computer model. Furthermore, they refute a recent attempt to deal with a class of retrieval problems within the decompositional framework. Bierwisch and Schreuder (1992) propose to solve the hyperonym problem (Levelt, 1989) by an inhibitory channel in the mental lexicon between a word and its hyperonyms. This predicts semantic inhibition by hyponyms, instead of the observed facilitation.