Cancer is one of the most frequent causes of death in Poland and in the world. The low efficacy of conventional treatment, as well as the high toxicity of the usual therapies, have stimulated the search for alternative methods. One of them is the deployment of oncolytic viruses. Oncolytic viruses have a natural ability to lyse tumor cells or can obtain this ability through certain modifications. The aim of virotherapy is to discover a virus that will lyse only tumor cells, and will not be dangerous to healthy cells, and moreover will not cause an undesirable response from the host’s immune system. Animal viruses with oncolytic abilities are very promising, because they are not pathogenic for humans and often show a high specificity for human cancerous cells.