Hyperventilation syndrome is a common and often disabling condition. Traditional treatment consists of reassurance and anxiolytic drugs. Hyperventilation is known to precipitate an asthmatic reaction. A retrospective review of patients with hyperventilation syndrome was performed to ascertain the frequency of asthma as well as the response to bronchodilator medication. Forty-seven patients were seen. Thirty-eight were tested, and asthma was proved in 36. Two additional patients had positive clinical responses with bronchodilators. Thus, asthma was identified in 38 of 47 consecutive patients seen for hyperventilation syndrome (80 percent), and asthma was proved in 36 of 38 of patients tested (95 percent). Hyperventilation syndrome was eliminated in 29 of 35 patients (90 percent) treated with a combination of explanation and bronchodilator treatment.