We have studied bronchial biopsies from 14 patients with newly diagnosed asthma (four men and 10 women), who had had asthma symptoms, on average, 7.4 months (range, 2 to 12 months) and from four control subjects. The patients had not received corticosteroids, disodium cromoglycate, or theophylline before the study. The bronchial biopsies were taken, using a rigid-tube bronchoscope under local anaesthesia, from two different airway levels: (1) inside the right upper lobe bronchus, and (2) at the opening of the right middle lobe. The specimens were prepared for both light and electron microscopy. The use of Slot grids 1 x 2 mm enabled a large area of the thin sections to be photographed and analyzed by applying a graphic Autocad program. There was an increase in the numbers of mast cells (p < 0.001), eosinophils (p < 0.05), lymphocytes (p < 0.05), and macrophages (p < 0.05) in the epithelium of patients with newly diagnosed asthma as compared with those in control subjects. In the lamina propria, these asthmatic patients had more eosinophils (p < 0.001), lymphocytes (p < 0.001), macrophages (p < 0.001), and plasma cells (p < 0.001) than did the control subjects. We conclude that, in asthma, an airway inflammatory process is present even at a clinically early stage of the disease. In the asthmatic airways, there are signs of a general inflammatory response caused by more than one cell type.