Recent reports have demonstrated that mouse and human fibroblasts can be directly induced to neurons through the lentiviral expression of three transcription factors Ascl1, Brn2 and Mytll (ABM).The limitation of this technology is that these genome-integration viruses may increase the risk of tumor formation.In this study, we used non-integrating adenoviruses carrying a different combination of transcription factors Asc11, Brn2 and Ngn2 (ABN) for the conversion of mouse embryonic and adult fibroblasts to neurons.