Twenty nine infants (8 females and 21 males) were included in our study and 8 of 29 infants were of premature birth. The youngest patient was 3 months old and the older fourteen months old. The beginning of the study started at least three weeks after the first bronchiolitis episode. Pulmonary function test was realized using body plethysmography (Babybody, Erich Jaeger, Germany). Same tests were performed at 18 and 24 months. At 30 and 36 months, pulmonary function was evaluated by measuring respiratory resistances using an oscillometry system and an occlusion system (Masterlab-IOS, Erich Jaeger, Germany). All respiratory tests were performed on patients in asymptomatic respiratory condition and at least one month apart from respiratory infection. If measured data showed an obstruction, a bronchodilator was inhaled to assess reversibility. When results were normal, a bronchial provocation test, using inhaled metacholine, was performed.