The gene for tumour necrosis factor (TNF) lies at the telomeric end of the class III region of the major histocompatibility complex (MHC). Polymorphisms within this gene have been implicated in the genetic background of a large number of common human diseases. Recently two polymorphisms, TNF +489 and +691, have been described in the first intron of TNF (+489, G to A transition; +691, G deletion) and disease associations have been reported; however, the pattern of linkage disequilibrium with other MHC alleles has not been studied. We have therefore studied the association of TNF alleles with HLA-DR, -DQ and -B alleles in 216 healthy individuals from the north of England. The frequencies of the uncommon alleles were 0.08 (+489A) and 0.05 (+691Gdel). The +489A allele is associated with carriage of DRB1*1104, DQB1*0301, B18 and B35. The +691Gdel allele is associated with carriage of DRB1*13 *11, DQB1*0301 and B44. Knowledge of the pattern of association, indicating probable linkage disequilibrium, between these TNF alleles may be useful in studies aimed at determining the role of this locus in the genetic background of the large number of diseases which show genetic associations with MHC haplotypes.