Pulse nuclear magnetic resonance (NMR) magnetization decay studies were performed on normal and cold cataractous rat lenses. Computer analyses of the decay curves have been interpreted to reflect two types of water within the lens that do not exchange rapidly. Upon lowering the temperature in the presence and absence of 5% acrylamide (a known agent that prevents the cold cataract phenomenon), significant differences in the relaxation rates of one water fraction were noted. 2H (NMR) spectra on young rabbit and human lenses showed temperature-related linewidth changes, which are significantly diminished in lenses incubated in acrylamide. 31P spectra also showed similar inorganic phosphate linewidth changes and also reflected progressive alterations in the metabolic state of these lenses. These studies demonstrate the potential of NMR methods for monitoring physicochemical parameters in the normal and cataractous mammalian lens.