Equations correlating sequence distributions of nonhomogeneous first-order Markovian copolymer systems have been derived. For systems where (r1r2) differs by a factor of 2 from unity, a cubic power series approximation in polymer composition is necessary to predict triads to a standard deviation of ∼ 0.001–0.003. This precision holds over fairly broad ranges of (r1r2) and distribution function moments. Prediction of kinetic factors from sequence distribution data requires such precision that any derived data are questionable. Where two catalysts are involved, at least one of which is non-Bernoullian, there does not appear to be a practical way to derive kinetic data from triad sequences. Such systems can simulate homogeneous Bernoullian systems very closely.