Over the last decade, immunotherapy approaches for the treatment of cancer have been investigated with renewed vigour, perhaps catalyzed by the clinical successes seen with monoclonal antibody and cytokine based therapies. The identification of tumor-associated antigens (TAAs) in multiple cancer types has enabled the development of targeted immunotherapies and allayed some of the safety concerns associated with the induction of deleterious autoimmune reactions. In addition to the TAA or therapeutic gene, the antigen delivery system is equally as important for the development of a successful cancer vaccine. One approach to induce a potent and targeted antitumor response is to use viruses to deliver the TAA to cells of the immune system. A diverse array of oncolytic viruses and recombinant viral vectors encoding numerous therapeutic genes or TAAs have been tested in pre-clinical studies and produced results which, in some cases, justify their clinical development as potential cancer immunotherapies. Within the last 5-10 years, many such recombinant vectors have made the transition from pre-clinical research to clinical development and it is these, which are given most weight in this review.