We used a combined behavioral and electrophysiological technique to test the hypothesis that storage of information is impaired in childhood autism. Endogenous event-related potentials associated with the random deletion of stimuli within a regular train of auditory or visual stimuli were examined in three autistic and three normal children. We found that all subjects were able to detect the stimulus deletions, but cortical potentials associated with stimulus omissions were smaller or absent in the autistic subjects. These results are consistent with dysfunction within the system that includes posterior parietal cortex and its connections with the mesolimbic temporal cortex and hippocampus.