This 28-day, double-blind, randomized study in 256 patients compared the efficacy and safety of mizolastine 10 mg daily with placebo in patients with seasonal allergic rhinoconjunctivitis. All four nasal symptoms (itch, rhinorrhoea, sneezing, obstruction) and three ocular symptoms (itch, tears, redness) were rated by investigators using both a 0-3 and a 0-9 rating scale. Compared with the placebo group total, nasal and ocular scores were all significantly lower in the mizolastine-treated patients at day 14 of the study (P = 0.0002-0.0009, using the 0-9 scale) and relief was maintained throughout the 4-week study duration. Patient diary total scores showed that mizolastine was effective from the first day of treatment. The 0-9 scale appears to be more sensitive than the 0-3 scale for rating symptoms of seasonal allergic rhinitis.