In this study lateral differences in tympanic membrane temperature (TMT) were explored as an index of cerebral lateralization. TMT posttask differences were examined for sustained attention to response tasks (SARTs) following the presentation of negative and neutral emotional picture stimuli. Right TMT changed significantly more from baseline TMT than did left TMT after participants performed SARTs, a finding consistent with previous research indicating right cerebral dominance for sustained attention and response inhibition. Moreover, there was a trend (p = .09) for a picture stimuli by hemisphere interaction, with right-left differences in TMT being greater after the presentation of negative pictures than after neutral pictures. This result is consistent with previous findings indicating right cerebral dominance of negative emotional processing. Overall, these results support TMT as a useful and very cost effective index of cerebral lateralization.