In vitro tests of cellular and humoral immunity were analysed by: T and B lymphocytes, T4 and T8 lymphocyte subsets, lymphocyte blast transformation tests with unspecified mitogenom--phytohemaglutinin, C3 and C4 components of the complement and circulating immune complexes at patients from 6 to 54 years old who suffered from atopic dermatitis without any other clinical symptom of atopy (so called "pure" atopic dermatitis). Parameters of cellular and humoral immunity were analysed in the active and quiescent phase of illness. The results were statistically analyzed by Student's "t" test and compared with results of the control group. In the active phase of illness IgE level in serum was statistically and significantly increased while other parameters of humoral and cellular immunity did not significantly differ in relation to control group. In certain percentage in the active phase of illness decreased values of serum's IgA, C3 component of the complement, number of T8 lymphocytes and lymphocytes transformation test were found as well as the increase of circulating immune complexes IgG, IgM and B lymphocyte. All laboratory tests were repeated in the quiescent phase of illness, when patients had no changes on the skin in at least one month period. It was found that some increased values of serum's IgE were normalised in the quiescent phase of illness. Besides increased serum's IgE in the active phase of illness, it was not possible to determine cellular and humoral immunity defect by tests in vitro at "pure" atopic dermatitis.