New gene therapies will prevent, cure, or more effectively treat many diseases that previously were unavoidable, incurable, or untreatable, or that responded to treatment only incompletely or was accompanied by numerous side effects. Gene therapy therefore will be in great demand. If it provides a cheaper alternative to existing medical interventions, it will be embraced by patients and readily offered by managed care plans and other third-party payers, such as Medicare and Medicaid. But in many cases, a gene therapy will increase rather than decrease health care costs. For example, it might be a more effective but also more expensive treatment than before. Or, it might target a disease for which there were no previous medical options, and thus no treatment cost. In these cases, third-party payers will resist paying for these new technologies, and this will lead to disputes that come before the courts.