OBJECTIVES: It has been clearly demonstrated that after donor-specific cell transfer the prolongation of allograft survival can be obtained, but the problem of how to inoculate cells remains unresolved. In this study, the effect of either portal venous (PV) or systemic intravenous (i.v.) inoculations of rat donor-specific spleen cells on subsequent renal graft survival was evaluated. METHODS: LEW recipients received 10(6) of spleen cells from allogeneic Fischer or syngeneic donors 30 days before kidney transplantation by either PV or i.v. routes. Animals from the control group obtained buffered saline by the same routes. RESULTS: Fischer grafts in nonimmunized LEW recipients were rejected after 9.6 +/- 1.3 days. In contrast, the immunization of the recipients by the pretreatment with donor spleen cells prolonged renal allograft survival significantly (p < 0.002). However, no difference in the graft survival was observed between animals inoculated with cells either by PV or by i.v. routes. In each studied group, long-time graft survival (> 100 days) was achieved in one case. CONCLUSIONS: These observations suggest that the effect of the various routes of allogeneic cell inoculations on subsequent organ graft survival time depends on the interval between the cell transfer and organ transplantation. Intravenous route seems to be as effective as PV route when transplantation is performed several days after donor-specific cell transfusion.