Crossmodal semantic priming paradigms compare responses to target stimuli in one sensory modality following presentation of semantically congruent or incongruent primes in another modality. Using one such paradigm with natural object stimulus pairs, congruent primes in both visual and haptic modalities have recently been shown to improve responses to auditory targets when compared with incongruent primes (Schneider et al., 2008, Experimental Psychology; IMRF 2008). Here we extended this investigation by comparing the effects of congruent and incongruent auditory primes on responses to visual targets. Moreover, in order to ascertain whether crossmodal congruency effects result from interference (in the case of incongruent primes) or from facilitation (with congruent primes), or both, we also compared responses in each case to a neutral control condition where visual targets were preceded by a meaningless visual prime. Eighteen healthy adult volunteers were asked to classify natural objects shown in degraded pictures as either large or small. Presentation of pictures was preceded by a short congruent or incongruent sound or by a small grey square. During the task, EEG was recorded from 68 electrodes. One-way repeated-measures ANOVAs showed significant differences between the three conditions (p<.01) in terms of both accuracy and response time (RT). Pairwise comparisons confirmed better performance both in accuracy and RT in the congruent condition compared with incongruent (p<.05). When compared with the control condition, performance was less accurate in the incongruent condition (p<.05), whereas RT was faster in the congruent condition (p<.05). No other pairwise comparisons were significant. This pattern of results suggests that both facilitation and interference processes contribute to crossmodal semantic priming. EEG data will be presented exploring the neurophysiological mechanisms of these effects.