Olefins are polymerized under solution polymerization conditions in the presence of the solid catalytic product resulting from removing the liquid components from the product resulting from admixing in an inert diluent and in an atmosphere which excludes moisture and oxygen (A) at least one hydrocarbon soluble organomagnesium compound; (B) at least one organic hydroxyl-containing compound; (C) at least one reducing halide source; (D) at least one transition metal (Tm) alkoxide.