Sarcomas are malignant cancers of connective tissues. They may be movable lumps under the skin or growths that deeply attach to underlying structures. The incidence of sarcomas has risen significantly since 1991, and vaccines (especially those for rabies and feline leukemia) appear to be associated with this increase. Complete removal of these tumors is nearly impossible since they are poorly defined and spread easily. Even in combination with radiation, the cure rate is low. Chemotherapy may be one of the remaining options for cats with this cancer. Ifosfamide is a chemotherapy drug that has proven effective against sarcomas in humans. Preliminary studies by our group have shown treatment with ifosfamide caused one patient with a large, inoperable tumor above the eye to have a dramatic reduction in the size of the tumor. The researchers will continue to evaluate ifosfamide in cats to determine the best dose and the response to the drug. If successful, this chemotherapy drug could make a major advance in the fight against vaccine-site sarcomas in cats.