Residence of B cells in the peritoneal cavity enhances their capability to migrate back into the peritoneal cavity. Ly5.1⁺ splenocytes were injected intraperitoneally into congenic Ly5.2⁺ wild-type recipients. Three hours (○) or 18 hours (●) after transfer, cells were isolated from the recipients' peritoneal cavity, and their migratory potential was assessed in competitive adoptive transfer experiments compared with freshly isolated wild-type Ly5.1⁺ splenocytes. The injected mixtures of differentially labeled cells were adjusted to contain equal numbers of Ly5.1⁺ B cells. One day after transfer, the number of transferred cells influenced by the peritoneal cavity (treated cells) compared with untreated splenocytes was determined by flow cytometry. Data represent the mean of 8 and 4 recipient mice analyzed for 3 hours and 18 hours, respectively. Error bars represent the SEM; PBL, peripheral blood lymphocytes. Statistical differences are indicated for the mean values and variances separately as follows: *P < .05; **P < .01; ***P < .001.