In this report, we describe the homing of hematopoietic stem cells (HSCs) to non-hematopoietic tissues in lethally irradiated (9Gy) hybrid mice transplanted intravenously with lin(-)/CD117(+) bone marrow cells from ROSA26 mice. The numbers of CFU-GM in spleen of irradiated transplanted mice were well above the levels found in non-irradiated group as early as day 8 after transplant. On 12th day regeneration of lymphocytes was observed, an increase in granulocytes was detected as late as on 33rd day. Transplanted cells containing lacZ gene were detected in recipient mice by histochemistry and their location in the thymus, liver, stomach and ileum was followed during 33days post-transplantation. On 8 and 33days post-transplantation, we found massive presence of donor (lacZ(+)) cells in the thymic cortex. Hematopoietic stem cell transplantation led not only to recovery of hematopoietic and lymphoid tissues but also facilitated recovery of the small intestinal mucosa, which was significantly damaged by ionizing radiation.