The skin of non-inbred white rats has been studied from birth up to 2 years of age. The amount of non-pigmented granular dendrocytes (AGD) (Langerhans cells) has been determined in the epidermis by means of reaction to ATP-as and lymphocytes. Mitotic activity (MA), DNA contents in basal keratinocytes, enzymatic activity of the energy metabolism in the derma of the papillary layer, amount of tissue basophils and presence of serotonin in them are estimated by means of the luminescent method. During the first month of life the amount of the AGD and lymphocytes in epidermis increases and there is a parallel decrease in the MA, in thickness of epidermis, in DNA contents of the basal keratinocytes. The distribution of the enzymatic activity of the energy metabolism in the epidermis becomes similar to that in mature animals. By the old age the amount of the AGD and lymphocytes decreases. The amount of the tissue basophils increases up to the 19th day of life, then it decreases, and especially noticeably--by the old age. Serotonin is revealed for the first time in the tissue basophils at the age of 16 days. Its contents increases quickly during the first month of life and remains constant up to the end of the observations. There is a certain parallelism in amount of AGD, epidermal lymphocytes and tissue basophils of the derma. Perhaps in the skin there is a local functional system: basal keratinocytes--AGD--intraepidermal lymphocytes--tissue basophil of the derma.