Oncolytic viruses are promising cytoreductive agents for cancer treatment but extensive human testing will be required before they are made commercially available. Here, we investigated the oncolytic potential of two commercially available live attenuated vaccines, Moraten measles and Jeryl-Lynn mumps, in a murine model of intraperitoneal human ovarian cancer and compared their efficacies against a recombinant oncolytic measles virus (MV-CEA) that is being tested in a phase I clinical trial. The common feature of these viruses is that they express hemagglutinin and fusion therapeutic proteins that can induce extensive fusion of the infected cell with its neighbors, resulting in death of the cell monolayer. In vitro, the three viruses caused intercellular fusion in human ovarian cancer cells but with marked differences in fusion kinetics. MV-CEA was the fastest followed by Jeryl-Lynn mumps virus while Moraten measles virus was the slowest, although all viruses eventually caused comparable cell death 6 days postinfection. Tumor-bearing mice treated with 10(6) or 10(7) pfu (one thousand times the vaccine dose) of each of the three viruses responded favorably to therapy with significant prolongations in survival. All three viruses demonstrated equivalent antitumor potency. Commercially available Moraten measles and Jeryl-Lynn mumps vaccines warrant further investigation as potential anticancer agents.