Doubrovin and colleagues report on a retroviral vector encoding the human norepinephrine transporter (hNET) that, when transduced into EBV-antigen specific T cells, permits quantitative in vivo imaging of the accumulation of adoptively transferred T cells in EBV⁺ tumors by PET or SPECT based on their selective uptake of radiolabeled metaiodobenzylguanidine (MIBG). Differential uptake of ^[123I]MIBG by transduced hNET-CD4⁺ T cells and ^[124I]FIAU by transduced HSV-TK-CD8⁺ T cells also permits independent, contemporaneous tracking of each T-cell population in the same animal by SPECT and PET, respectively. This human reporter system should not be immunogenic and may prove useful for clinical imaging of transduced cells following adoptive transfer or transplantation. For details, see the article by Doubrovin and colleagues on page 11959 of this issue.