Objective. To study the effects of two kinds of Chinese herbal medicine

Radix angelicae sinensis（RAS）（当归）and Shuanghuanglian（SHL）（双黄连） on chronic Pseudomonas aeruginosa（PA）lung infection in a rat model mimicking cystic fibrosis（CF）. Methods.Rats were divided into RAS

SHL and control groups. All rats were challenged intratracheally with alginate embedded PA and the treatments with herbal medicine started on the same day of challenge. The drugs were administered subcutaneously once a day for ten days and the control group was treated with sterile saline.The rats were sacrificed two weeks after challenge. Results. Significantly improved lung bacterial clearance（P<005

P<001） and milder macroscopic lung pathology （P<0005） were found in the two treated groups compared to the control group. In the SHL treated group

the neutrophil percent in the peripheral blood leukocytes（P<005）

the antiPA IgG level in serum （P<005）

the incidence of lung abscesses（P<0005） and the incidence of acute lung inflammation（P<005） were significantly lower than in the control group. The RAS treatment reduced fever（P<005）

decreased the incidence of lung abscesses（P<0005） and lung mast cell number （P<005）

and lowered antiPA IgG1 level in serum（P<005） when compared to the control group. The antiPA bacterial activity test in SHL was weakly positive whereas in RAS it was negative. Conclusion.The treatment with both herbal medicines could increase the resistance of the rats against PA lung infection and they therefore might be potential promising drugs for stimulation of the immune system in CF patients with chronic PA lung infection.