Background: There appears to be an association between sinusitis and asthma. The effect on bronchial hyperresponsiveness of clinical therapy for sinusitis in children may help to decipher whether sinusitis and asthma are independent manifestations of the same disease.Objective: To evaluate the effect of clinical treatment fur sinusitis in patients with rhinitis and/or asthma on symptoms and on bronchial hyperresponsiveness to methacholine.Methods: Open label, randomized, non-treatment control in a teaching hospital in Sao Paulo, Brazil. Forty-six atopic and 20 normal children were studied. The atopic children consisted of 18 with allergic rhinitis (12 without sinusitis and 6 with sinusitis), and 28 children with rhinitis with asthma (13 wit...