A number of new medications for treatment of asthma and chronic obstructive pulmonary disease have been developed in recent years. However, serious issues persist in the management of these illnesses. Prevalence, morbidity, and mortality of asthma are increasing despite the introduction of these new agents. Airflow obstruction is only partially reversible in chronic obstructive pulmonary disease, and drug treatment can only mitigate disability incompletely. Drug toxicity is also an important concern. The five classes of agents (beta-adrenergic agonists, anticholinergic agents, theophylline, cromolyn, and corticosteroids) available for treatment are examined in this review, emphasizing efficacy and toxicity. Less commonly used agents and newly developed compounds that are still investigational are also discussed.