Contingent Negative Variation (CNV), an event related slow EEG potential is thought to be influenced by `attention' because of the nature .of the paradigm used to generate it. `Attention' can describe selective attention or arousal-2 related but separate concepts. Previous explanations of CNV in these terms are inadequate because experimenters have failed to manipulate these variables independently. This study employs an alternative design that enables predictions to be made as to how different individuals' CNV's will vary in accordance with their previously determined abilities to selectively attend and to be aroused. Groups of subjects (`good' and `poor' selective attenders and those with `high' and `low' arousal potential participated in a CNV experiment involving a condition of distraction. Changes in CNV amplitude were predicted such that a model could be formulated in terms of selective attention or arousal but not both. While not conclusive, the results favoured a model of CNV in terms of arousal.