Twenty patients with allergic rhinitis and/or asthma sensitised to Dermatophagoides pteronyssinus were studied. On two consecutive days they underwent methacholine challenge and allergen bronchial challenge. 72 h after allergen challenge, fibreoptic bronchoscopy with bronchial (BL) and bronchoalveolar (BAL) lavage was performed. Specific IgE antibodies were measured both in serum and in BL from 14 patients. Both BAL and BL cell differentials were similar in patients with isolated early response to allergen and in patients with dual response. Patients with dual response to allergen showed higher levels of antigen specific IgE antibodies in BL than patients with isolated early response, while IgE levels in serum were similar in the two groups.