Stuttering is a poorly understood communication disorder with a 1% global prevalence. Recently, there has been a resurgence of interest in a neurogenic origin for the disorder, although no research has established clear neurological differences between "developmental" (stuttering onset in childhood) stutterers and nonstutterers. We have used xenon 133 single-photon emission computed tomography to study regional cerebral blood flow (rCBF) in 20 stutterers. Analysis revealed global, absolute flow reductions. Relative flow asymmetries (left less than right) were identified in three hemispheric regions: anterior cingulate and superior and middle temporal gyri. Milder changes were found in the left inferior frontal gyrus. Stutterers had rCBF values below median for either anterior cingulate or middle temporal gyri. With one exception, severe stutterers had rCBF values below median for the anterior cingulate gyrus. All stutterers with rCBF values above median in the cingulate gyrus had rCBF values below median in the middle temporal gyrus, and severity of their disorder was either mild or moderate. Our findings suggest that stuttering is a neurogenic disorder involving recognized cortical regions of speech-motor control.