In the present experiments, a multimodality regimen was developed that included an anti-T cell receptor R73 monoclonal antibody and the pharmacologic agents brequinar (BQR), cyclosporine (CsA), and sirolimus (rapamycin; RAPA) to prolong the survival of small bowel (SB) allografts. BQR was the most potent single drug: the 4.0 or 8.0 mg/kg/day BQR doses delivered every second day (q.o.d.) per gavage for 28 days prolonged the survival of Brown Norway (BN; RT1n) SB allografts in Lewis (LEW; RT1l) recipients from a mean survival time of 10.6 +/- 1.9 days in untreated controls to 29.2 +/- 5.8 days, respectively (both P < 0.001). When treatment was extended to 56 days, 8.0 mg/kg/q.o.d BQR produced a mean survival time of 83.8 +/0 33.8 days (P < 0.001), with 2/5 hosts surviving more than 100 days. In a host-versus-graft model, BQR (8.0 mg/kg/q.o.d) delivered for 28 days with CsA (2.0 mg/kg/day) and RAPA (0.04 mg/kg/day) delivered intravenously for 14 days prolonged the survival of BN SB grafts in LEW recipients to 54.4 +/- 21.0 days (P < 0.001). Extending triple-drug therapy to 42 days induced the prolongation of SB allograft survival to greater than 100 days in 5/7 recipients. Although pretransplant perfusion of the grafts with R73 mAb was ineffective alone, the combination of graft perfusion and a 28-day course of BQR (8.0 mg/kg/q.o.d) in the GVH model indefinitely prolonged LEW graft in F1 recipients. Alternatively, indefinite survival of SB allografts ( > 100 days; P < 0.001) was achieved by the combination of a 14-day course of a triple-drug regimen using each agent at subtherapeutic doses, namely BQR (2.0 mg/kg/q.o.d.), CsA (2.0 mg/kg/day), and RAPA (0.04 mg/kg/day). The state of transplantation tolerance is these hosts was documented by the acceptance of donor-type but not third-party heart allografts.