Objective Toinve stigate the role of peripheral immunocompetent lymphocytes during the immunere sponse in the innerear1 Methods Sensitized lymphocytes from peripheral blood, neck lymph nodes and spleen of three groups of donor animals, i1e1, group A immunized intradermally with keyhole limpet hemocyanine (KLH) and both inner ears challenged with KLH, group B received only KLH intradermally without inner ear challenge, and group Cused as control, were isolated and labelled with 51 Cr1 The labelled lymphocytes were injected intravenously into the recipients1 They were immunized intradermally with right inner ears challenged with KLH1 Twenty to 24hlater, the radioactivities in the temporal bones of the recipients were assayed to detect the infiltration of labelled cells1