Abnormally high levels of IgE are produced in various diseases, including atopic eczema, and a functional decrease in the T-lymphocyte population occurs at the same time. T-cell function has been studied in a group of asthma patients with high, normal and low IgE levels and in a control group. T-cell function appears to be reduced in asthmatic patients with high concentrations of IgE when skin tests are performed with Candida antigen (P less than 0.05). There was also a decline in the lymphocyte transformation tests with candida antigen in autologous serum (P less than 0.05), although not in foetal calf serum. The responses to in vivo tests with streptokinase-streptodornase were normal, as was the response of the lymphocytes to PHA.