alpha,omega-Vinyl-terminated butadiene oligomers can be generated through the cross-metathesis of ethylene and high molecular weight 1,4-polybutadiene catalyzed by the complex RuCl2(=CHPh)(PCy3)(2). The effect of varied ethylene pressure is studied in order to obtain the highest conversion to the monomer 1,5-hexadiene. A dramatic increase in yield of this monomeric diene is realized relative to previous published attempts utilizing a well-defined group VI metal alkylidene in the same chemistry. Traces of side products are observed, and alternate mechanisms for their formation were proposed.