Nuclear magnetic resonance (NMR) imaging methods have been applied to study the behavior of crumb rubber materials in asphalt. Pieces of natural tire rubber and styrene-butadiene tire rubber were immersed in a high acid-content asphalt and heated at 170 degrees C for different periods of time up to 48 h. After heating, 3D images were acquired during cooling and after the samples were at room temperature. Images of the natural and styrene butadiene rubber in asphalt, taken at room temperature after heating, showed a progressive loss of image intensity with increased heating time. From an NMR perspective the loss of signal could be due to the rubber having become more rigid as a result of heating, or because of possible dissolution of the rubber by the asphalt. However, images of the same samples, taken while the samples were at an elevated temperature, showed that the crumb rubber materials had swelled in the presence of the asphalt. Samples of the same materials in the absence of asphalt were heated and imaged in the same manner. Images of these samples showed only a small loss of signal with heating and hardly any swelling.