With the recent development of new catalysts based on specific metallocenes, ethylene polymers with a narrow molecular weight distribution and comonomers placed homogeneously in the polymer chain have been accessible. In particular, bridged amido complexes can be used to integrate defined long-chain branches into the macromolecule. These complexes lead to homogeneous branched polyethylenes (HBPEs). These long-chain branches provide various new properties. Polymer blends of these polymers with high-density polyethylene (HDPE) were manufactured in a twin-screw extruder and characterized by their thermal, mechanical, and processing properties. The HDPE/HBPE blends with low and high comonomer content in the HBPE have been studied over the total range of composition of the blend components, and the influence of the octene content of the HBPEs on the properties of the mixtures was shown for two different blend compositions. Furthermore, the properties of the blends for HDPE and long-chain branched HBPE were compared with HDPE blends of polyethylenes without long-chain branching but similar molecular parameters in relation to the HBPE. The differences were discussed on the basis of the density of the tie-molecules of the polymers. © 1997 John Wiley & Sons, Inc. Adv in Polym Techn 16: 135–145, 1997