Interleukin 10 (IL10) is a powerful TH2-cell cytokine that inhibits lymphocyte replication and secretion of inflammatory cytokines. The genetic associations of polymorphisms in IL10 with clinical manifestations of tuberculosis (TB) were examined in a large number of patients with clinical TB infection (n = 459) and normal controls (n = 871). One common promoter SNP (IL10 -592 A>C) was found to be significantly associated with decreased risk of TB manifestation. The frequency of the "C"-bearing genotype was higher in normal controls than in patients with clinical TB infection (P = 0.005, OR = 0.69). A summary of the genetic effect of IL10 -1082 A>G, the other nearby promoter SNP, in other ethnic groups is also presented.