A kinetic model to describe the propylene polymerization behavior of ansa-metallocene catalysts was derived. The model can predict n-ad stereosequence distributions, polymer crystallinity, and related properties as well as distinguish between extremes in kinetic behavior expected for such catalysts. In particular, where polymer microstructure is sensitive to changes in [C3H6], the model can provide reliable estimates of kinetic parameters of interest, including ratios between rates of some of the significant reaction steps involved in polymer microstructure formation. The model is applied to a description of the polymerization behavior of some simple symmetrical [Me2C(Cp)(Flu)MCl2; M = Zr, Hf] and unsymmetrical [Me2Y(Cp)(Ind)MCl2; M = Zr, Hf; Y = C, Si] ansa-metallocene catalysts, activated with methyl aluminoxane. With the former two catalysts, the Zr catalyst operates very close to the kinetic quenching limit where chain inversion (br chain back-skip) is slow compared to monomer insertion, while for the Hf analogue, these two processes have more comparable rates. In the more complicated, unsymmetrical systems, both Zr- and Hf-based systems (Y = Si) operate under conditions where inversion is much faster that propagation, whereas for the I-If catalyst (Y = C), intermediate behavior is observed, and the corresponding Zr complex (Y = C) produces poly(propylene) where propagation is faster than inversion.