An increasing amount of evidence suggests that both cerebral hemispheres contribute to the comprehension of semantic relations. A literature review of language abilities after right hemisphere (RH) damage reveals abnormalities in the interpretation of lexical items that have alternate meanings (Chiarello, 1991). Two major theories have been proposed to account for the lexical-semantic deficits observed in RH damaged (RHD) individuals, namely the "suppression deficit" and the "coarse semantic coding" hypotheses. By exploiting the theoretical linguistic distinction of lexical ambiguity into homonymy, metaphor and metonymy, the present investigation attempts to directly contrast the predictions of the two hypotheses. To this end, two on-line priming studies were developed, each comprising two experiments conducted with RHD patients, individuals with nonfluent aphasia subsequent to left hemisphere damage (LHD) and non-brain-damaged control participants (NC).