Four picture-word interference experiments aimed to test the role of grammatical class in lexical production. In Experiment 1 target nouns and verbs were produced in presence of semantically unrelated distractors that could also be nouns and verbs. Participants were slower when the distractor was of the same grammatical category of the target. To rule out the semantic hypothesis that the effects were due to objects versus actions semantic dichotomy rather than to grammatical class, Experiment 2 was conducted. Participants named target verbs in presence of unrelated action nouns and verbs. The results evidenced a grammatical category effect. Finally, in Experiments 3 and 4, morphologically not derived materials were used to verify the role of morphological information. The results evidenced a syntactic effect independent from morphology. Taken together the results supported the hypothesis that grammatical class information plays a crucial role in lexical production.