Alternative medicine and complementary therapies are being increasingly used in the United States for treatment or prevention of a variety of diseases. The lack of side effects and likely lower costs compared with conventional medications are major attractions to these treatments. Despite the general belief, use of herbal medicines and folk remedies can cause severe side effects and toxicities. Physicians' knowledge of herbal medicines and their potential toxicities are generally limited. In particular, pulmonary toxicities and respiratory side effects occur after the use of complementary medicines. Familiarity of physicians with this subject is important to identify and treat potential pulmonary toxicities of complementary medicines. Interstitial pneumonitis, eosinophilic pneumonia, bronchiolitis, lipoid pneumonia, asthma, and pulmonary hypertension are potential side effects of complementary medicines. The subject of pulmonary toxicity and complementary medicines is reviewed.