Abstract
Surface markers of lymphocytes from peritoneal fluid of the guinea pig are studied and compared with those of lymphocytes from thymus, peripheral blood and spleen. The great majority of peritoneal lymphocytes form rosettes with rabbit red cells and bear receptors for Fc of IgG (T Fc+ cells). Lymphocytes with these characteristics are poorly represented in blood, thymus and spleen. Guinea pig peritoneal lymphocytes can be compared, as far as surface markers are concerned, with lymphocytes from human cerebrospinal fluid and transudates.