Bronchial hyperreactivity is a condition in which the airways show a much greater bronchoconstriction response to provocative stimuli than what is normal. The stimuli may be specific (different allergens) or non-specific (exercise, infection, cold, air, ozone, kerosene or a variety of inhalant irritants). The normal control of the airways is regulated by: parasympathetic cholinergic nerves, sympathetic adrenergic nerves and non-adrenergic bronchodilator system. The activity in all these pathways regulates bronchomotor tone which is affected by many different reflexes. Such changes play a role in hyperreactivity. Exposure to allergens is another cause of inflammation and specific hyperreactivity which may increase the degree of non-specific bronchial reactivity. Inheritance has been implicated in bronchial hyperreactivity according to animal experiments and human twins studies. Calcium ions are involved in most cellular processes and their role in bronchial hyperreactivity is related to defects in calcium regulation and metabolism. Based on this speculation, calcium antagonist drugs have been used in the treatment of bronchial asthma, though no clinical improvement has been observed by most authors.