<p>A mammalian subject having a tumor is treated by a method comprising administering an effective amount of a Newcastle disease virus, wherein the virus is administered to the subject in one or more cycles; and at least one cycle comprises administering sequentially one or more initial doses of from 1.8x10<SUP>10 </SUP>PFU to 4.8x10<SUP>10 </SUP>PFU of the virus per square meter of patient surface area followed by administering one or more subsequent doses of from 2.4x10<SUP>10 </SUP>PFU to 1.2x10<SUP>11 </SUP>PFU of the virus per square meter of patient surface area.</p>