Background The highly polymorphic interleukin 10.G (IL10.G) microsatellite located in the promoter region of the interleukin-10 (IL-10) gene exerts a positive transcriptional regulatory effect on IL-10 gene expression and correlates with the in vitro IL-10 secretion. This study was conducted to investigate whether IL10.G microsatellite is associated with the incidence and /or the outcome of severe sepsis.Methods One hundred and fifteen patients with severe sepsis who had been treated at the intensive care unit of the university hospital were studied. One hundred and forty-one healthy individuals served as controls. IL10.G microsatellite genotyping was performed with the following two methods: fluorescent based polymerase chain reaction (PCR) techniques and silver staining of the amplified DNA fragment in polyacrylamide gel. Alleles were defined according to the size of the amplified DNA product.Results Ten alleles and 36 genotypes were detected both in the patients with severe sepsis and in the healthy controls. Allele IL10.G9 and allele IL10.G13 were the commonest alleles with the frequencies of 32.6% and 21.3% respectively in the patients with severe sepsis, and 34% and 27% respectively in the healthy controls. The allele frequencies of IL10.G microsatellite were neither different between the patients with severe sepsis and the healthy controls (P > 0.05), nor between survivors and non-survivors (P > 0.05). However, the frequency of one common allele IL10.G13 was slightly lower in the patients with severe sepsis than in the healthy controls (21.3% vs 27%, P > 0.05), and the frequency of allele IL10.G9 was slightly higher in the non-survivors than in the survivors (37.1% vs 28.1%, P > 0.05).Conclusion IL10.G microsatellite may neither contribute to the susceptibility to severe sepsis nor to the fatal outcome of severe sepsis.