The present invention is within the field of oncolytic virotherapy. Oncolytic virotherapy is a strategy using viruses, naturally occurring or genetically modified, to selectively target and destroy tumor cells while leaving surrounding non-malignant cells unharmed Here, an engineered respiratory syncytial virus (RSV), with the NS1 gene deleted (NS1 gene-deficient RSV, ΔNS1 RSV), kills prostate cancer cells, but does not affect normal human cells.