Using E and EAC rossette assays, T and B lymphocytes were quantitated in patients with atopic eczema. Adult patients had percentages of T lymphocytes at the lower end of the range of normal. When evaluated as a group, their mean percentage was significantly lower than that of controls. B lymphocytes were present in normal percentages. Absolute numbers of both T and B lymphocytes were significantly decreased. These data suggest that there is a defect in cell-mediated immunity in the atopic population that may be important in the pathogenesis of the disease.