The integrity of the blood-brain barrier (BBB) can be noninvasively monitored by magnetic resonance imaging (MRI). Conventional MR contrast agents (CAs) containing gadolinium are used in association with MRI in routine clinical practice to detect and quantify BBB leakage. Under normal circumstances CAs do not cross the intact BBB. However due to their small size they extravasate from the blood into the brain tissue even when the BBB is partially compromised. Here we describe an MR method based on T1-weighted images taken prior to and after CA injection. This MR method is useful for investigating BBB permeability in in vivo mouse models and can be easily applied in a number of experimental disease conditions including neuroinflammation disorders, or to assess (un)wanted drug effects.