To clarify the organic changes and pathophysiology of the lungs in intractable asthmatics, the dynamic states of pulmonary ventilation and perfusion were analyzed in 15 bronchial asthmatic in the stable state using (133)Xe gas ventilation scintigraphy and (99m)Tc-MAA lung perfusion scintigraphy, respectively. Dysfunction of pulmonary ventilation and impairment of pulmonary perfusin were significantly severer in intractable asthmatics than in non-intractable asthmatics (p<0.01, P<0.05, respectively) and those of asthma caused by aging. Late onset asthmatics with a long duration of disease tended to show severe impairment of pulmonary perfusion. Above all the longer the duration of the disease the severer became the impairment of pulmonary perfusion in late onset intractable asthmatics (LOIA). These findings suggest that the progression of irreversible organic changes of lungs in LOIA is involved in the severity of brochial asthma.