Estimates of the loss to Medicare and Medicaid programs due to fraud range from 10 to 25 percent of the almost $100 billion expended annually. Victims of medical fraud rarely know they have been bilked or that an injury was the consequence of unnecessary or unwarranted medical procedures. Nonetheless, criminal activities of physicians can come to the attention of other physicians and be reported to authorities. Professional Standard Review Organizations (PSRO's) are local physician groups that determine whether services are medically necessary and rendered in accordance with professional standards. PSRO's represent an attempt by the government to identify and sanction aberrant physicians. PSRO's do not always function effectively, however, because of the confidentiality of the doctor-patient relationship and the gap between the PSRO and the local medical community. Physicians are able to deflect the possibility of criminal action by blaming errant actions on administrative errors. Some efforts have been made in the last 10-15 years to increase investigate resources. For example, the Office of Inspector General was created within the U.S. Department of Health and Human Services to insure the integrity of government health programs. Several factors, however, limit the effectiveness of fraud prevention efforts, not the least of which is the government's fear of alienating the medical profession through regulatory sanctions and criminal punishment and reducing the number of physicians participating in Medicare and Medicaid programs. Another concern of program administrators with fraud and abuse efforts involves undermining public confidence in Medicare and Medicaid. For physician behavior to be treated criminally requires that prosecutors believe conviction is likely.