The study was designed to investigate efficacy and safety of Astragalus membranaceus (AM) in the treatment of patients with seasonal allergic rhinitis (SAR). AM is an active component in the herbal and mineral complex (HMC) registered in Croatia as a food supplement Lectranal®. The study was designed as a 6-weeks, double-blind, placebo-controlled clinical trial and conducted in 48 adult patients with a moderate to severe SAR. The treatment efficacy was evaluated by the mean change in the symptom score (TSS), quality of life (QoL), specific serum IgE and IgG, nasal eosinophils, and physicians' and patients' global evaluation. Compared to placebo, HMC significantly decreased the intensity of rhinorrhea while for other primary efficacy variables the treatment groups did not differ. In contrast, investigators and patients equally judged the treatment with HMC as more efficacious. In addition, the analysis of changes from baseline inside the groups for TSS, QoL, and 4 main symptoms of SAR were strikingly in favor of the active treatment. In patients with SAR due to weed pollen allergy HMC significantly improved primary variables, reflective TSS and QoL. The study revealed a significant number of positive signals indicating the therapeutic effectiveness of the HMC in patients with SAR which should be further tested in larger, multicentre trials with more patients. Copyright © 2009 John Wiley & Sons, Ltd.