AbstractUsing a 32‐echo imaging pulse sequence, T2relaxation decay curves were acquired from five white‐ and six gray‐matter brain structures outlined in 12 normal volunteers. The water contents of white and gray matter were 0.71 (0.01) and 0.83 (0.03) g/ml, respectively. All white‐matter structures had significantly higher myelin water percentages (signal percentage with T2between 10 and 50 ms) than all gray‐matter structures. The range in geometric mean T2of the main peak for both white and gray matter was from 70 to 86 ms.T2distributions from the posterior internal capsules and splenium of the corpus callosum were significantly wider (width is related to water environment inhomogeneity) than those from any other white‐ or gray‐matter structures. Thus, quantitative measurement and analysis ofT2relaxation reveals differences in brain tissue water environments not discernible on conventional MR images. These differences may make shortT2components reliable markers for