The T and B lymphocytes in frozen sections of skin obtained from patients with various lympho-infiltrating disorders of the skin were identified using an immunofluorescent technique. Anti T-lymphocytes serum was used as a T marker and anti Ig GMA serum and HL-B alloantigens as B markers. The method proved to be efficient in preliminary experiments. Specimens were obtained from patients with lymphocytic infiltration of the skin (LIS), lymphadenosis benigna cutis (LBC), lymphoma cutis (LC) and mycosis fungoides (MF). In LIS and LBC the dominant cell was found to be the T lymphocyte, suggesting that a local immune reaction of the cell-mediated type may play a role in their etiology.