The purpose of the study is to determine if inhaled iloprost given four times daily can improve symptoms and lung function in adults with mild asthma.

Animal studies have suggested that prostacyclin may downregulate allergic inflammation, thus providing the scientific basis for trials of inhaled prostacyclin agonists such as iloprost for the treatment of asthma. This study will examine the tolerability of four times daily iloprost on asthma symptoms and pulmonary function over a two week treatment period.

Inclusion Criteria:

1. Age 18-60
2. History of asthma controlled by inhaled rescue medication (albuterol, levalbuterol etc) and/or inhaled corticosteroids
3. Ability to give informed consent
4. Ability to perform pulmonary function tests
5. Ability to tolerate the initial Ventavis inhalation
6. Ability to comply with the study protocol

Exclusion Criteria:

1. Cigarette smoking
2. Concomitant serious disease such as diabetes, hypertension, coronary heart disease, other lung disease, cancer (other than skin cancer)
3. Pregnancy or lack of contraception (hormonal or barrier)
4. Allergies or intolerance to inhaled iloprost
5. Participation in other ongoing research studies
6. Any psychological problem that the investigators believe might interfere with the conduct of the investigation.
7. Cigarette smoking
8. History of bleeding disorder, use of anticoagulants
9. Viral upper respiratory tract infection within the last 6 weeks
10. Table of upper limit for steroid use Beclomethasone dipropionate HFA-MDI 480 Budesonide DPI 1200 Flunisolide HFA-MDI 640 Fluticasone HFA-MDI 440 Fluticasone DPI 500 Mometasone DPI 440 Triamcinolone 1500 (Table adapted from EPR3, daily doses are in micrograms) Asthmatics requiring higher doses of inhaled corticosteroids than those given above, or using oral steroids, leukotriene modifiers, mast cell stabilizers, omalizumab, theophylline or long acting beta agonists will be excluded.
11. .Any screening laboratory blood test value outside the normal range will exclude the individual from the study, though an isolated abnormal value could be retested at an interval of no less than a week.