The present invention provides methods for inducing regression of tumors in human subjects, the methods utilize a modified mesogenic strain of Newcastle disease virus (NDV) with modified F protein cleavage site, which is non-pathogenic to poultry (lentogenic), but exhibits oncolytic properties. The disclosed methods provide safe, effective and reliable means to induce regression of a tumor in an individual in need thereof. These methods overcome the drawbacks of using pathogenic strains of viruses for human therapy.