In support of its research and development mission and security of its facilities, the Department of Energy (Department) maintains a significant inventory of explosives. Our inspection revealed problems with handling and storing explosives at each of the four contractor-operated sites we visited, potentially increasing the risk of harm to personnel and infrastructure. For instance, we found that, contrary to established practice designed to minimize the impact of inadvertent detonation, Savannah River Site and Idaho National Laboratory performed explosive shipment inspections during peak traffic hours at populated main gates rather than at remote areas and/or during non-peak traffic hours. We also observed that excess combustible and non-combustible materials were being stored in explosives bunkers; incorrect bunker placards and fire symbols were posted on bunkers and buildings; and, excess explosives waste was not being disposed of timely. We found that Department management had not focused the attention needed to ensure that the responsible facilities contractors properly implemented Department policies for handling and storing explosives, as required. Also, contractor officials charged with managing and safeguarding explosives had not ensured compliance with various aspects of the DOE Explosives Safety Manual. In response to our findings, Department management generally concurred with our recommendations, and proposed and took corrective actions to improve the safety at explosives storage and operating facilities.