In this study children with recurrent wheezing (>/= 2 episodes in the last 6 months)and aged less than 2 years will be enrolled as outpatients. They will undergo lung function evaluation by Rint and by assessment of the flow curves at baseline and after 4 weeks of treatment with Montelukast 4 mg/day. Symptom dairies will be filled by parents during the study period.

Patients aged less than 2 years with recurrent wheezing. At visit 1 patients with symptoms will be enrolled and the study explained. They will return home with bronchodilator therapy.

Within 1 week they will return for visit 2 to start a run-in period with bronchodilators prn and they will fill dairies with symptoms and drug use. Skin prick test will be evaluated at that time.

At visit 3 after 1 week of the run-in period they will start therapy with Montelukast 4 mg for 4 weeks, using bronchodilators prn and filling diaries.

The final visit will be after four weeks with re-evaluation of the lung function

Inclusion Criteria:

• Age between 6-24 months
• Patients with recurrent wheezing (at least 2 episodes in the last 6 months)
• Patients with symptoms at enrollment

Exclusion Criteria:

• Chronic respiratory diseases (cystic fibrosis, chronic lung disease) symptoms at visit 1 that require hospital admission