The purpose of this study was to demonstrate the possibility of delivering autologous bone marrow precursor cells into the spinal cord via lumbar puncture technique (LP) in patients with spinal cord injury (SCI). Magnetic resonance imaging provides a noninvasive method for studying the fate of transplanted cells in vivo. Considering these propositions, we studied magnetic resonance tracking of autologous bone marrow CD34(+) cells labeled with magnetic nanoparticles delivered into the spinal cord via LP in patients with SCI. Sixteen patients with chronic SCI were enrolled and divided into two groups; one group got their own labeled-CD34(+) cells injected into the spinal cord via LP (n = 10); the others received an injection, but it contained magnetic beads without stem cells (controls, n = 6). CD34(+) cells were magnetically labeled with magnetic beads coated with a monoclonal antibody specific for the CD34 cell membrane antigen. Magnetic resonance images were obtained by a standard turbospin echo-T2 weighted sequences before and 20 and 35 days after post-transplantation. The median number of CD34(+) cells injected via LP was 0.7 x 10(6) (range 0.45 to 1.22 x 10(6)). Magnetically labeled CD34(+) cells were visible at the lesion site as hypointense signals in five patients of the labeled-CD34(+) group 20 and 35 days after transplantation; these signals were not visible in any patient of the control group. We suggested for the first time that autologous bone marrow CD34(+) cells labeled with magnetic nanoparticles delivered into the spinal cord via LP technique migrated into the injured site in patients with chronic SCI.