The RBC immune function of 88 patients with epidemic haemorrhagic fever (EHF) was examined kinetically with complement-labeled yeast method established by Guo Feng. The results showed that the percentage of RBC c3b receptor rossette, activity of RCIA-enhancing factor and c3 in sera of patients during the 3 different phases of EHF were markedly lower than those of the normal controls, while the percentage of RBC IC rossete, activity of RCIA-inhibiting factor and CIC in sera of the patients were manifestly higher (P less than 0.01). The change of all the indices observed above was most apparent in oliguric phase. This suggested that RBC immune function is lowered in the process of EHF.