The morphological structure of words, in terms of their stem morphemes and affixes, could influence word access and representation in lexical memory. Three experiments were carried out to explore the attributes of event-related potentials evoked by different types of priming. Morphological priming, with pairs of words related by their stem (hijo/hija [son/ daughter]), produced a sustained attenuation (and even a tendency to positivity) of the N400 shown by unrelated words across the three experiments. Homographic priming (Experiment 1), using pairs of words with a superficially similar stem, but without morphological or semantic relation (foco/foca [floodlight/seal]), produced an initial attenuation similar to the morphological pairs, but which rapidly tended to form a delayed N400, due to the impossibility of integration. However, orthographic priming (rasa/rana [flat/frog]) in Experiment 2 does not produce attenuation of the N400 but an effect similar to that of unrelated pairs. Experiment 3 shows that synonyms advance more slowly than morphological pairs to meaning coherence, but finally produce a more positive peak around 600 msec.