Asthma is a chronic disabling respiratory disease that can be triggered by a variety of factors, including allergens, respiratory infections, psychological factors, occupational agents, exercise, atmospheric pollutants, and drugs. The asthma syndrome has been treated for decades according to a “one-fits-all” treatment strategy based on bronchodilators and steroids. With the availability of new forms of treatment targeting the different pathomechanisms of the asthma syndrome, such as anti-immunoglobulin E and cytokine-targeting therapies, the interest in biomarkers that can dis criminate different forms of asthma according to their pathomechanisms has increased. This review attempts to provide an overview of protein biomarkers in asthma and how they might be used to discriminate different forms of asthma that may respond positively to sophisticated new targeted therapies.