AbstractWe investigated central nervous system correlates of simple phobie fear, Regional cerebral blood flow (rcBF) was measured using position emission tomography(PFT) in eight volunteers with symptomatic spider phobia that were exposed to visual phobogenic and neutral stimuli Diazepam (0.1 mg/kg body weight i.v.) or placebo was administered under double blind conditions after initial PFT scans. The PFT scans were then repeated. The presence of fear was confirmed by rating procedures and increased number of nonspecific electrodermal fluctuations and by higher heart rate during phobic than during neutral stimulation. Phobic as compared to neural stimulation elevated the retional to whole brain (relative) CBF in the secondary visual cortex but reduced relative rCBF in the hippocampus, prefrontal, orbitofrontal, ttemporopolar, and posterior cingulated cortex. Dia/epam treatment did not affect the relative rCBF or the subjective or physiological fear indices. The observed rCPF pattern replicates our previous findings in snake phobics (M. Fredrikson et al.[1993]Psychophysiology, 30, 127, 131 G. Wik et al. [1993]Psychiatry Research (Neuroimaging), 50, 15–24) and indicated that fear and anxiety affect cortical areas outside the classic limbie system area