Compositions of several high-molecular-weight (>10(6) g mol-1) water-soluble copolymers have been determined using direct-polarization magic-angle spinning (d.p.m.a.s.) C-13 nuclear magnetic resonance (n.m.r.). Comonomers were studied that comprised acrylamide and sodium 3-acrylamido-3-methylbutanoate, sodium 2-acrylamido-2-methylpropanesulfonate, diacetone acrylamide or isopropylacrylamide. A copolymer of sodium 2-acrylamido-2-methylpropanesulfonate and 2-acrylamido-2-methylpropanetrimethylammonium chloride was also included. The technique is rapid and provides copolymer compositional analysis with accuracies close to those obtained by conventional elemental analysis and solution n.m.r. techniques. Spectral resolution is excellent and d.p.m.a.s. n.m.r. allows shorter acquisition times and smaller sample size. The technique is applied to a variety of acrylamide copolymers including polyelectrolytes, polyampholytes and hydrophobically associating polymers. The results are compared to copolymer compositions obtained from elemental analysis and solution C-13 n.m.r. spectroscopy.