This multicenter post-marketing surveillance study examined the course of characteristic signs and symptoms and the tolerability of myrtol standardized (Gelomyrtol/Gelomyrtol forte) in 511 children (4 to 12 years of age) with acute and chronic sinusitis, bronchitis and sinubronchitis. The choice of dose and formulation (120 mg or 300 mg myrtol stand) accounted for the patients' age and body weight. The following signs and symptoms were evaluated before and after 1 and 2 weeks of treatment: impaired nasal respiration (blocked-up nose), pain upon pressure on the trigeminal nerve endings, headache, sensitivity of the paranasal sinuses, presence of mucus in the pharynx. At the end of the observation period, the physicians, the patients themselves and their parents judged efficacy of the medication. In more than 90% of the children, trigeminal pain, headache, paranasal sensitivity, and mucus in the pharynx had disappeared after two weeks of treatment. In more than 60%, impaired nasal respiration and difficulty to evacuate sputum were no longer observed. The incidence of adverse drug reactions was low: less than 1%. The efficacy was judged to be very good or good by the majority of physicians, patients and parents. In spite of their young age, most children (> 80%) experienced no difficulty in swallowing the capsules.