Study of Levalbuterol, Racemic Albuterol and Placebo in Subjects Twelve Years of Age and Older With Asthma

Inclusion Criteria * Willing and able to comply with the study procedures and visit schedules * Male or female, at least 12 years of age * Female subjects 12-60 years of age must have a negative serum pregnancy test at study start. * Women of child bearing potential must be using an acceptable method of birth control * Have a documented diagnosis of asthma for a minimum of 6 months prior to study start * Must have stable baseline asthma and have been using a B-adrenergic agonist, and/or anti-asthma anti-inflammatory medication, and/or OTC asthma medication for at least 6 months prior to study start * Must be in good health with the exception of their reversible airways disease and not suffering from any chronic condition that might affect their respiratory function * Must have a chest X-ray that is not diagnostic of pneumonia, atelectasis, pulmonary fibrotic disease, pneumothorax, chronic obstructive pulmonary disease, etc. * Must be able to complete the diary cards and medical event calendars reliably on a daily basis, understand dosing instructions, and demonstrate how to use the MiniWright PEF meter. Exclusion Criteria * Female subject who is pregnant or lactating * Have participated in an investigational drug study within 30 days prior to study start, or who is currently participating in another clinical trial * Subject whose schedule prevents him or her from taking the first daily dose of study medication and/or starting study visits before 9 AM * Subject who has travel commitments during the study that would interfere with trial measurements or compliance * Have a history of hospitalization for asthma within 45 days prior to study start, or who is scheduled for in-patient hospitalization, including elective surgery * Have a known sensitivity to levalbuterol or racemic albuterol, or any excipients in any of these formulations * Subject using any prescription drug with which albuterol sulfate administration is contraindicated * Subject with currently diagnosed life-threatening asthma * History of cancer (exception: basal cell carcinoma in remission). * Subject with hyperthyroidism, diabetes, hypertension, cardiac diseases or seizure disorders that currently are not well controlled by medication * History of substance abuse or drug abuse within 12 months preceding study start * Subject with greater than 10 pack year history of cigarette smoking or use of any tobacco products within 6 months of study start * Documented history of bronchopulmonary aspergillosis or any form of allergic alveolitis * Have suffered from a clinically significant upper or lower respiratory tract infection in the 2 weeks prior to study start * Subject who is a staff member or relative of a staff member