Hexadecene-1 was used as comonomer with ethylene in a slurry polymerization with Ziegler-Natta catalysts. Hexadecene contents remained at less than 4 wt % in ethylene/hexadecene-1 copolymers. When butene-1 was also present in the polymerization, hexadecene-1 contents were significantly higher. With hexadecene content of 11 wt %, the terpolymer density was 910 g/dm**3. The effect of butene addition was significantly smaller with less than 10 carbon atoms containing alpha -olefins.