The 13C-1H shift-correlated two-dimensional NMR spectroscopy (CSCM) is used to study ethylene-propylene copolymers. By this means, the 1H NMR spectra of these copolymers can be fully interpreted. The assignments are much more complex than previously thought. Because of overlapping resonances, a direct determination of the copolymer composition cannot be made. However, the use of a first-order Markovian probability model gives not only information on composition, but also the comonomer reaction probabilities.