Functional neuroimaging affords unique insights into the neural activity of intact human brains. In previous studies, presenting speech to subjects without an explicit task demand (so-called ‘‘passive’’ listening) produced strong activations in bilateral dorsolateral temporal cortex (DLTC) that is both extensive and symmetrical [Wise et al., Brain 114, 1803–1817 (1991)]. Thus such results support the hypothesis that the DLTC of both hemispheres is involved in the acoustic and phonological processing of speech. This is contradictory to conventional understanding that the left temporal lobe, particularly Wernicke’s area, is responsible for speech identification and recognition. A study using positron emission tomography was performed which aims to contrast speech processing with a similarly complex signal; speech- and signal-correlated noise analog were presented in a listening task. Correlations specific to speech stimuli were located symmetrically in anterior regions of both superior temporal sulci. The only asymmetry waas a left-lateralized response to speech in the posterior superior temporal sulcus, corresponding closely to structural asymmetry on the subjects’ magnetic resonance images. These results are discussed in relation to the role of the right hemisphere in recovery of speech comprehension after left hemisphere-damage.