To investigate the changes of thyroxin and monocyte human leukocyte antigen-DR expression in senior patients with sepsis and explore their clinical significance.According to the 2001 SCCM/ESICM/ACCP/ATS/SIS international sepsis definitions, 125 senior patients with sepsis free of thyroid conditions were divided into non-severe sepsis group (n=86) and severe sepsis group (n=39), with another 30 healthy subjects as the control. Thyroid function was assayed by chemoluminescence method in these patients and monocyte HLA-DR expression was determined by flow cytometry.Compared with the control group and non-severe sepsis cases, the levels of free T3 (FT3), free T4 (FT4), T3, T4 and monocyte HLA-DR expression were significantly lower in severe sepsis cases (P0.05). The non-severe sepsis cases showed significantly lower levels of FT3, FT4, T3, T4, TSH and monocyte HLA-DR expression than the control group (P<0.05). In severe sepsis group, the levels of FT3, FT4, T3, T4 and monocyte HLA-DR expression showed significant differences between the fatal cases and surviving cases (P<0.05).The levels of thyroxin and monocyte human leukocyte antigen-DR expression are obviously lower in senior patients with severe sepsis, and their detection may well indicate the severity of the condition and help make prognostic judgment.