Bronchial biopsy specimens from subjects with intermittent or "early" asthma were compared with specimens taken from healthy subjects. Patients with early asthma included those with seasonal asthma and occupational asthma. There was a small but statistically significant increase in the thickness of the subepithelial extracellular matrix protein tenascin in subjects with seasonal and occupational asthma compared with control subjects. Collagen types IV and VII were increased only in patients with occupational asthma. Eosinophils were the only inflammatory cells that were significantly increased in subjects with seasonal asthma compared with control subjects. These data show that inflammation is present in the airways of patients with early asthma, and the increase in tenascin expression in the basement membrane zone suggests that structural changes are also initiated at an early stage of the disease.