Although the role of eosinophils, mast cells, and T cells in asthma has long been recognized, several reports suggest that neutrophils may also be involved. In most studies of people with mild asthma, neutrophil numbers in the airways are not different from controls. However, in severe asthma, including asthma deaths, neutrophils are usually raised. Furthermore, most pediatric studies suggest that neutrophils are raised in some children, in particular in the young or infantile wheeze group. Measurements of inflammatory mediators in the airways of asthmatic subjects suggest that neutrophils are activated.