Huntsville Hospital (the Hospital) (operating in Huntsville, Alabama) complied with Medicare billing requirements for 178 of the 277 inpatient and outpatient claims we reviewed. However, the Hospital did not fully comply with Medicare billing requirements for the remaining 99 claims, resulting in net overpayments of $24,000 for the audit period. Specifically, 7 inpatient claims had billing errors, resulting in net overpayments of $18,000, and 92 outpatient claims had billing errors, resulting in overpayments of $6,000. These errors occurred primarily because the Hospital did not have adequate controls to prevent the incorrect billing of Medicare claims within the selected risk areas that contained errors. On the basis of our sample results, we estimated that the Hospital received overpayments of at least $203,000 for the audit period.