Objective To study the cellular immunity function and clinic of HFRS patients treated by cimetidine.Methods CD+_4 T lymphocyte,CD+_8 T lymphocyte and NK cell activity were determined by flow cytometer.Results Treating HFRS patients with cimetidine could shorten fever period(P0.05).Conclusion IFN-? and ribavirin+thymosin can treat HFRS patients effectively,three therapies have equal effect.