In a randomised single blind trial the Chinese herbs Shuang Huang Lian were evaluated for the treatment of acute bronchiolitis. Children with acute bronchiolitis and serological evidence of recent respiratory syncytial virus infection were studied in a tertiary hospital in Harbin, China. The 96 children were randomised into three treatment groups: herbs, herbs with antibiotics, and antibiotics alone. The herbs were prepared by the medical school pharmacy and administered daily by intravenous infusion for seven days. The main outcomes, assessed blindly, were symptomatic improvement in cough, fever, wheezing, chest signs, and duration of stay in hospital. The mean duration of symptoms from the start of treatment was 6.2 (confidence interval 5.6 to 6.9) days in the two groups treated with herbs compared with 8.6 (confidence interval 7.5 to 9.8) days in the group treated with antibiotics alone. The mean reductions in duration of clinical manifestations for treatment with antibiotics alone compared with herbs were: from 3.1 to 1.5 days for fever, 9.1 to 6.1 days for cough, 6.5 to 4.1 days for wheezing, and 7.2 to 4.9 days for chest crackles. No adverse effect of Shuang Huang Lian herbal treatment was detected. In conclusion, this study confirms Chinese experience with Shuang Huang Lian that it is safe and effective, and warrants further study.