In both children and adults, rhinovirus (RV) infections remain a major cause of exacerbations in asthma. With the use of both in vitro models of RV infection and experimental models of asthma exacerbation in humans, insight into the precise role of RV in this process has been obtained. RV infects the lower airways, and the virus itself, together with the immune response to the virus, leads to increased airway obstruction in some patients with asthma. Defects in the immune response to RV in these patients may also lead to increased symptom severity and to more significant exacerbations. Work further investigating the mechanisms of exacerbation caused by RV infection will ultimately lead to new modalities of treatment and possibly prevention of this common and significant cause of acute asthma.