Water proton transverse (T,) relaxation measurements in whey, egg, gelatin, and soybean sols and gels were determined. TZ relaxation in protein sols and gels was a single exponential process, except for oil containing sols which showed a two-phase behavior. The relaxation rates (l/r,) increased linearly with concentration of either protein or oil. For samples containing protein which underwent an irreversible denaturation upon heating, T, relaxation times were longer in the sols than in the gels. In gels, the variation of the Ta relaxation times with temperature was interpreted in terms of an exchange between labile protein protons and water protons.