Islet transplantation is a potential treatment for type 1 diabetes. Currently, islet graft survival is measured using invasive methods to determine blood glucose, insulin, and C-peptide levels, even though these variables have limited value. To trace beta-cell survival and functional status, we constructed an adenovirus/adenoassociate virus hybrid vector (Hyb-DR) carrying two reporter genes, luciferase and green fluorescent protein (GFP), linked by the internal ribosome entry site and driven by the rat insulin II promoter. Luciferase activity increased and positive GFP expression was observed in beta-cell lines (MIN6N8 and INS-1E) infected with Hyb-DR. Using an in vivo imaging instrument, the GFP signal was detected in the flanks of nude mice 2 weeks after transplanting Hyb-DR-infected MIN6 cells into the kidney capsule. Coinfection of Hyb-DR with plasmids carrying beta-cell-specific transcription factors also resulted in expression of luciferase and GFP in the non-beta-cell lines (HepG2, FL83B, and YGIC5). Thus, the dual reporter system provided quantitative and visual information about the functionality of the islet mass and activation of the insulin gene.