A means for local passive transfer of DTH in the mouse has been discovered and partially characterized. Briefly, peritoneal exudates (PE) are induced with incomplete Freund's adjuvant 5 to 7 days after immunization with antigen (usually picGPA) emulsified with complete Freund's adjuvant. Five days later, PE cells are harvested and transferred with soluble antigen into a hind footpad of a naive mouse. Antigen-specific swelling is defined as the change in diameter of footpads over the 24 hr after injection of PE cells plus immunizing antigen minus change in diameter of footpads injected with PE cells plus control antigen. Antigen-specific footpad swelling of 20 to 80% was found in contrast to meager swelling when lymph node or spleen cells were used. The magnitude was dependent on dose of both cells and antigen over a broad range (1 to 12 X 10(6) cells, 1 to 100 micrograms of antigen per recipient). Specific swelling was reduced to nil after treatment of PE cells with anti-theta serum, indicating T cell dependence. Carrier specificity of the response was similar to DTH in the guinea pig. Time course and histology are compatible with a DTH response as well. The superiority of PE cells in local transfer of DTH and the modest requirements of this murine local transfer system provide potent tools for identification of the cell(s) that mediate DTH and their interactions. This system, in addition, should provide a sensitive indicator of immunomodulating activity in cellfree supernatants.