Blends of polyethylene and poly(vinyl chloride) were prepared on a Brabender Plasticorder, and attempts were made to improve the very inferior physical properties of the product. The blends were found to have domain structures, and it was shown that their physical properties could be improved very considerably if the domain sizes could be reduced drastically. However, in melt blending, there was a limit to the reduction of domain sizes. A noticeable improvement in properties was achieved through the use of various fillers and crosslinking agents. Small changes in crystallite size and percentage crystallinity were observed where certain additives were used. It appeared that the additives that were most effective in enhancing physical properties acted by improving load transfer at the interface between the two polymer phases.