To determine the feasibility of using the C.B-17 scid/scid (severe combined immune deficient, SCID) mouse as a recipient of human synovial xenografts, we have engrafted human synovium under the renal capsule of SCID mice, and determined synovial graft survival and histologic characteristics 4 to 7 wk after tissue implantation. Both normal and inflammatory synovial tissue grew well in SCID mice and maintained histologic and phenotypic components of the fresh synovial tissue before implantation. However, the number of T cells in synovial grafts decreased after implantation. To determine whether leukocytes could migrate to human synovial xenografts, either allogenic or autologous PBMC were injected in the peritoneum of SCID mice bearing synovial xenografts. We found that 7 days after i.p. injection of autologous or allogeneic PBMC, injected T cells had selectively migrated to human synovial grafts and to SCID mouse lymph nodes. Our data demonstrate that normal and inflammatory human synovial tissues will grow in SCID mice and serve as recipients for autologous and allogenic peripheral blood human T cells injected i.p. into engrafted mice.