Recent advances of nanotechnology in clinical settings have spurred the development of various complex engineered nanoparticles (NPs). NPs share characteristics with ultrafine particles (UFPs; <1 μm) that can cross the pulmonary epithelium and disturb cardiovascular functions. Since these particles are injected directly into the blood stream, it is imperative to clarify whether NPs disrupt cardiovascular functions similar to UFPs. Therefore, we investigated whether engineered polyethylene glycol (PEG)-coated aluminum NPs for biomedical uses disturb cardiovascular functions in healthy mice. Mean arterial blood pressure (MAP) was measured in mice chronically instrumented with telemetric blood pressure transducers, and NPs were administered intravenously (10 mg kg(-1)). The NPs caused a prolonged lowering of MAP 7 days after injection (119.3 ± 3.3 vs. 97.4 ± 7.5 min(-1)), with no effect on the endothelial function as revealed by normal endothelial function of small vessels mounted in a myograph.