The aim of this study was to investigate whether a physiological measure of impaired use of context could be obtained in people with Asperger's Syndrome (AS). The experimental paradigm employed was the use of electroencephalography to measure the detection of semantic incongruity within written sentences, as indexed by an N400 event-related potential. Whilst the seven controls appropriately demonstrated N400 potentials only to semantically incongruent stimuli, the seven participants with AS inappropriately demonstrated N400 potentials to congruent stimuli. These results are compatible with the possibility that the participants with AS did not use the context within sentences to predict the final word of the sentences.