PURPOSE: To obtain a treating agent for bronchial asthma containing 4- carbamoyl-1-β-D-ribofranosylimidazolium-5-olate as an active component, effective especially for late response and post-late response asthma and having low toxicity and high safety.

CONSTITUTION: This composition for treating bronchial asthma contains carbamoyl-1-β-D-ribofranosylimidazolium-5-olate (general name: mizoribine) as an active component. The composition is useful for treating especially bronchial asthma exhibiting late asthmatic response or post-late asthmatic response and severe or intractable steroid-dependent asthma. The treating agent has low toxicity and high safety, and it is capable of being administered orally for a long time and excellent in practical performance.