Acute exacerbations of asthma are often triggered by airways infection and a proportion of these infections are due to bacteria. We know that a group of patients with asthma have chronic airways infection with Haemophilus influenzae and this may be related to poor symptom control and more frequent exacerbations. Our aim is to look at the frequency of positive bacterial cultures of sputum in patients with acute exacerbation of asthma in whom sputum culture has been done and compare this to patients with non-infective respiratory diseases. The second aim is to assess the frequency with which Haemophilus is isolated in comparison to other bacterial species and see how these differences correlate with different types of asthma.