Abstract: Recombinant strains of avian paramyxovirus (APMV), such as Newcastle disease virus (NDV), are provided. Also provided are compositions comprising them, and methods of using them to lyse tumor cells and to treat cancer. In certain aspects, genetically-engineered viral strains that incorporate therapeutic transgenes are also provided. The recombinant viruses may be used in accordance with methods of providing enhanced oncolytic efficacy and delivering an oncolytic virus to tumors present in a patient. Also provided are methods for identifying a recombinant virus as an oncolytically-effective agent.