Omalizumab is the first of a new generation of targeted asthma therapies. This monoclonal antibody against IgE is now licensed for use in atopic asthma. The majority of asthmatics are well controlled with conventional therapies. However, there remains a cohort of patients with severe refractory asthma, despite currently available treatments ( approximately 5-10% of asthmatics), which account for approximately 50% of direct expenditure on asthma care. This article examines the evidence for both clinical and cost-effectiveness of omalizumab in patients with severe asthma and gives a 5-year view on the likely role of omalizumab in clinical practice.