The exceptional properties of a new class of linear polymeric hydrocarbons, obtained by the polymerization of alpha-olefins, are described. The high melting paints, the high degree of crystallinity, the low solubility, and the special mechanical properties of these polymers are attributed to a particular regularity of structure, due to the existence, in each macromolecule, of a long sequence of asymetric carbon atoms, all having the same steric configuration. It is suggested that this special type of order of asymetric carbon atoms in linear macromolecules be called "isotactical."