All relevant C-13 NMR signals of two series of seven homogeneous ethylene-propylene copolymers were used to fit the second-order Markov reactivity ratios of the catalysts and the theoretical feeds. The copolymers cover a very broad range of comonomer incorporations, from about 10 to 93%, and show only primary (1,2) insertions. For both series, solutions are found with reliabilities >> 99.5%. The reactivity ratios, r(112) = 2.54, r(121) = 0.12, r(212) = 2.05, and r(221) = 0.29 for the used Zirconocone and r(112) = 1.69, r(121) = 0.32, r(212) = 1.56, and r(221) = 0.51 for the hafnocene, provide direct information about the metallocenes, the kinetics, and the chain microstructure. With these results, the direct peak method demonstrates that the use of all relevant C-13 NMR peaks enables accurate second-order Markov modeling, revealing subtle differences between copolymers. (c) 2006 Wiley Periodicals, Inc.