The mechanical properties of polypropylene depend critically on the crystallizability of the chains, which depends in turn on their stereochemical structures. These dependences were investigated using Monte Carlo methods to generate chains having various stereochemical sequences and then scrutinizing parallel arrays of these chains to look for matches in isotactic stereochemistry that could lead to the formation of crystallites. The fraction of such units in matches, for example, gives a direct measure of the degree of crystallinity expected for the specified degree of isotacticity. Other quantities of interest obtainable in this way were the natures of the sequence distributions themselves, melting points, free energies of fusion, interfacial free energies, and moduli (calculated on the basis of the crystallites acting as crosslinks within an elastomeric network structure).