The regional cerebral blood flow (rCBF) in 19 patients with multiple sclerosis (MS), 10 with a relapsing remitting course and 9 with a progressive course, was examined by single photon emission computed tomography (SPECT) using technetium-99m hexamethylpropyleneamine oxime ([99mTc]-d,l-HM-PAO) as flow tracer. Nine age-matched volunteers served as controls. Low rCBF in the frontal grey matter correlated with neurological disability (p < 0.01), low frontal grey and white matter perfusion correlated with impaired cognitive functions (p < 0.02), and low rCBF in the occipital regions correlated with impaired visual functions (p < 0.03) in the MS population. A relationship was also found between reduced parietal white matter perfusion and the duration of the disease (p < 0.005). Patients with progressive MS had significantly reduced rCBF in the frontal grey matter compared with relapsing remitting MS patients and controls (p < 0.05). No other rCBF differences were found. As a diagnostic tool in MS, SPECT-[99mTc]-d,l-HM-PAO was found to be insensitive.