A new sequence is described to measure the cross-correlation rates between the chem. shift anisotropy of the carbonyl carbon-13 nucleus and the dipole-dipole interaction between this carbonyl and the alpha-proton in proteins. The sequence is based on the sym. reconversion principle and is insensitive to exptl. errors and to violations of the secular approxn. The cross-correlation rate depends on the backbone angle y. The advantages and limitations of the sequence are discussed. [on SciFinder (R)]