A growing body of data suggests that the emotional dimension of a stimulus can be processed without conscious identification of the stimulus. The arousal system could be activated by unrecognised biologically significant stimuli through simple physical stimulus features related to threat, without any evaluation of the meaning of the stimulus. However, unconscious processing of emotionally laden words cannot rely only on perceptual features but must include some analysis of symbolic meaning. The first aim of the present study was to assess whether masked (unrecognised) aversive words can elicit enhanced skin conductance responses (SCRs), a major autonomic index of emotional arousal, in normal participants. Our second aim was to determine whether any autonomic activation related to affective value of words is independent from access of this value to consciousness. Thus, the presentation duration of masked aversive and neutral words was determined, for each participant, in such a way that (1) identification was precluded, (2) valence discrimination was at chance, as indicated by performance in a forced-choice two-alternative task and by confidence ratings of the responses, and (3) emotional and neutral words were not detected differentially. SCRs were recorded during masked and unmasked presentations of both types of word. SCRs elicited by unmasked words, and also by masked words, were of greater magnitude when the words were emotional than when they were neutral. Consequently, in normal participants, autonomic activation can be a discriminative marker of the affective dimension of unrecognised verbal material in the absence of conscious valence identification.