Lymphocyte chemotaxis was studied in a blind-well chamber assay by measuring the passage of 51Cr-labeled cells through a polycarbonate filter with a pore size of 5 micron. Monocyte-depleted lymphocytes were divided into T cells (E receptor-positive lymphocytes) and non-T cells. T lymphocytes showed pronounced migration after exposure to leukotriene B4 (LTB4) and casein, and weak migration after exposure to N-formyl-methionyl-leucyl-phenylalanine (FMLP). Non-T cells showed strong migration after exposure to FMLP, but weak migration after exposure to casein and LTB4. Supernatants of homogenized suction blisters from normal skin did not induce active migration. However, if the epidermis came from an area overlying a positive tuberculin skin reaction, there was a significant migration mostly of T, but also of non-T cells. Supernatants from phytohemagglutinin (PHA)-stimulated lymphocyte cultures also contained lymphocyte chemotactic factor(s), which, however, had an effect only on T lymphocytes. Purified protein derivative of tuberculin (PPD)-stimulated lymphocytes did not produce chemoattractants either for T or for non-T cells. These studies show that lymphocytes can show active, directed migration following exposure to well-known chemotaxins for granulocytes and monocytes although their migrational capability differs for different subpopulations. Epidermis overlying a cell-mediated immune reaction (tuberculin) contains epidermal lymphocyte chemotactic factor(s). This factor(s) may be of importance for the type of cell infiltrate occurring in certain dermatologic disorders.