The 17-residue peptide FKLGGRDSRSGSPMARR derived from myelin basic protein, containing an epitope encephalitogenic in rhesus monkey, has been studied in aqueous solution by high-resolution one- and two-dimensional carbon and proton nuclear magnetic resonance spectroscopy. The resonances of the spectra from both nuclei were assigned with the aid of two-dimensional correlated spectroscopy, pH and solvent titrations, and one-dimensional spin-decoupling techniques and by comparison of the spectra of the heptadecapeptide with those of a phosphorylated form of the peptide, the pentadecapeptide FKLGGRDSRSGSPMA, and the nonapeptide FKLGGRDSR. Amide proton temperature coefficients, coupling constants, 13C- spin-lattice relaxation times, and nuclear Overhauser effect data suggest the existence of three structured regions comprising residues 3-6, 7-12, and 12-14 in the solution conformations of the encephalitogenic heptadecapeptide.