This study will evaluate the usefulness of a new procedure for evaluating asthma in children. The method measures the pH (a measure of acidity and alkalinity) of exhaled breath condensate (water vapor created by the lungs). The condensate contains products of the lungs that may be associated with lung inflammation. Investigators will determine if the pH of the exhaled breath condensate correlates well with known asthma indicators, such as number of hospitalizations, school absenteeism, use of rescue medication, and others. Test results will be compared with findings from healthy normal volunteers. No experimental treatments or medicines are used in this study. Patients who require treatment for their asthma will receive standard care with medicines approved by the Food and Drug Administration and used widely in the United States.