Tumor necrosis factor (TNF)-alpha and TNF-beta are proinflammatory cytokines that have been implicated in the pathogenesis of several autoimmune diseases. The aim of this investigation was to determine whether a determinant in the first intron of the TNF-beta gene (TNF-beta(+252)) and two promoter-region polymorphisms of the TNF-alpha gene (TNF-alpha(-308) and TNF-alpha(-238)) affect susceptibility to multiple sclerosis (MS). DNA samples from 133 Caucasian MS patients and 148 healthy controls from Norway were genotyped for several polymorphic determinants, using polymerase chain reaction-based restriction fragment length polymorphisms (PCR-RFLP) methods. TNF-beta(+252) genotypes were significantly associated with MS: The frequency of TNF-beta 2,2 was increased (p = 0.00009) while the frequency of TNF-beta 1,2 was decreased (p = 0.0012) in MS patients as compared to controls. TNF-alpha genotypes were not associated with MS. These results suggest that the TNF-beta gene plays a significant role in the etiopathogenesis of MS.