Many studies have investigated the fate of adoptively transferred lymphocytes in recipient mice, although little is known of the sites where these transferred cells reside at particular time points. Using flow cytometry, we analyzed the trafficking pattern of adoptively transferred naive B cells into the lymphoid organs of syngeneic B-cell-deficient (microMT) mice. Within the first 24 h of transfer, the location of B cells was highly dependent on the mode of B-cell transfer. When B cells were injected subcutaneously into microMT mice, they showed a different trafficking pattern from cells administered into the peritoneal cavity or injected intravenously. After subcutaneous transfer into the thigh, the greatest number of B cells was detected in the popliteal lymph node nearest to the injection site, whereas the lowest number was detected in the axillary lymph node opposite to the injection side. Within the first 24 h of either intraperitoneal and intravenous injection, B cells were found in approximately equal numbers in the lymph nodes and the spleen. Two days later, the B-cell distribution in the lymphoid organs appeared to be independent of the mode of B-cell transfer. A transient decrease in the numbers of splenic and lymph node B cells occurred 9 days after B-cell transfer (a decrease from 70 to 87%) prior to the outgrowth of B cells that occurs 21 days after transfer. These studies are useful for understanding the numbers of B cells that may be required in adoptive transfer studies and their potential cellular interactions at particular physiological sites based on the route of cell transfer.