The hydration of vimentin isolated from the cortex of bovine lenses was studied by thermal analysis. Differential scanning calorimetry between ––30, and 30°C provided the freezable water content, and thermogravimetric analysis up to 105°C yielded the total water content. The difference between the two gives the nonfreezable water content (bound water) as a function of concentration. The nonfreezable water content of the polymerized vimentin is higher than that of the monomeric vimentin. This behavior is exactly the opposite of that of actin. This difference is explained on the basis of different modes of supramolecular assembly in the two cytoskeletal bodies.