Proinflammatory cytokines (interleukin [IL]-1beta, tumor necrosis factor [TNF]-alpha, and IL-6) and soluble intercellular adhesion molecule-1 (sICAM-1) were measured in paired cerebrospinal fluid (CSF) and serum samples from patients with subacute sclerosing panencephalitis (SSPE), multiple sclerosis (MS), or other neurologic diseases (OND) by ELISA. IL-1beta was significantly increased in CSF of the SSPE group compared with levels in the MS or OND group. IL-1beta CSF/serum ratios were higher in the SSPE than in the MS or OND group. TNF-alpha and IL-6 levels were similar in the 3 groups. CSF sICAM-1 was higher in the SSPE group than in the MS or OND group. sICAM-1 CSF/serum ratios were higher in the SSPE than the OND group. The increased CSF/serum ratios of IL-1beta and sICAM-1 in SSPE indicate synthesis of IL-1beta and sICAM-1 in the central nervous system and may be important in the pathogenesis of disease.