An attenuated oncolytic vaccinia virus encoding the light-emitting fusion protein Renilla luciferase-Aequorea green fluorescent protein (RUC-GFP) with potential bioluminescent and antineoplastic activities. Upon administration, light-emitting oncolytic vaccinia virus GL-ONC1 specifically enters tumour cells due to the permeable nature of the tumour vasculature. Once inside the cell, the virus replicates, resulting in tumour cell lysis and the release of mature viral particles into the tumour microenvironment. Released viral particles may then infect and destroy neighbouring tumour cells. In addition, the release of tumor-associated antigens (TAAs) by lysed tumour cells into the bloodstream may activate the immune system to mount a cytotoxic T lymphocyte (CTL) response against the tumor. The expression of RUC-GFP by this agent allows for both detection and monitoring of virally infected tumour cells in vivo and vitro with luciferase-mediated bioluminescence imaging and fluorescence imaging techniques.