L-MTP-PE alone or with ifosfamide significantly improved the disease-free survival of relapsed osteosarcoma (OS) patients. Both IL-1α and IFNα improved the response rates to VP-16 chemotherapy in relapsed OS. Two nude mouse models were developed (for OS and Ewing’s sarcoma) to study the properties that influence metastases and to evaluate therapeutic strategies. We demonstrated the in vivo efficacy of liposomal 9-nitrocamptothecin given by aerosol delivery against OS lung metastases. A phase I trial is now underway with a future goal to initiate a phase II trial in relapsed OS patients. We demonstrated that nasal delivery of an adenoviral vector containing the IL-12 gene resulted in inhibition of pulmonary metastases and regression of microscopic tumors.