The efficacy and safety of Kampo preparation Sho-seiryu-to were studied in a joint double-blind trial in comparison with a placebo. The study was carried out on 220 patients with perennial nasal allergy at 61 hospitals. Granules in a dose of 3 g were administered 3 times daily for 2 weeks. Moderate to high improvement was recorded in 44.6% of the treated patients and in 18.1% of those receiving placebo. The difference is significant (p <0.001). Side effects were noted in 6.5% of the treated patients and in 6.4% of the controls (not a significant deference). The side effects were mild and had no influence on the daily life of the patients.