Leukocyte chemotaxis studies were performed in 14 patients with atopic dermatitis. Monocyte chemotactic responsiveness (MCR), polymorphonuclear leukocyte (PMN) chemotactic responsiveness (PCR), and patient serum inhibition of normal monocyte chemotaxis were evaluated. The most common defect noted was depressed MCR. This was found in 8 of the 14 patients and was associated with a chemotactic inhibitor in the serum of 5 of 6 of the 8 with depressed MCR whose sera were so tested. Depressed PCR was found in 3 of 10 patients studied. Ten of the 14 patients had depressed chemotaxis of at least one cell type. Depressed chemotaxis was not related to the presence of infection, to the serum IgE level, or to the severity of the eczema, and it could not be produced in vitro by incubating normal cells with histamine or IgE myeloma. These studies demonstrate a high frequency of leukocyte chemotactic abnormalities in patients with severe atopic dermatitis. Elucidation of the clinical significance of the leukotactic abnormalities observed and determination of whether they are basic or secondary to the disease process must await further study.