The U.S. Customs and Border Protection’s (CBP) Non-Intrusive Inspection (NII) program is vital to securing the Nation’s borders while facilitating efficient flow of legitimate trade and travel. CBP uses NII equipment to screen cargo and conveyances at our Nation’s land, sea, and air ports of entry. In fiscal year 2014, CBP awarded six contracts and one interagency agreement valued at approximately $90.4 million to perform preventive and corrective maintenance of NII equipment. We performed this audit to determine whether maintenance is being performed on CBP’s screening equipment in accordance with contractual requirements and manufacturers’ specifications. CBP monitored NII operations using methods such as conducting daily meetings to discuss NII availability and reviewing field office submissions of utilization reports. However, CBP has not ensured that contractors perform preventive and corrective maintenance on its screening equipment in accordance with contractual requirements and manufacturers’ specifications. This deficiency occurred because CBP has not verified that maintenance is performed in accordance with manufacturers’ specifications, evaluated contractors’ performance, and assessed the reliability of maintenance data. Without a process to validate maintenance data and to evaluate and assess that NII equipment is being repaired and maintained in accordance with manufacturers’ specifications, CBP’s NII equipment may not be repaired and maintained to retain full functionality and maximum useful life.