The miscibility of LLDPE and LDPE blends and the influence of mixing temperature (T-mix) are discussed. Adequate amounts of antioxidants were added during melt blending. Dynamic and steady shear measurements were carried out at 190 degreesC in a Rheometrics Mechanical Spectrometer 800. The dependence of rheological properties on blend composition indicated that blends of LLDPE (butene) and LDPE mixed at 190 degreesC and 220 degreesC are only partially miscible; immiscibilty is likely to occur around the 50/50 composition and in the LDPE-rich blends. Blends at 190 degreesC are likely miscible in the LLDPE-rich range. increasing T-mix did not improve the miscibility of LLDPE/LDPE blends at 190 degreesC or influence the dynamic shear properties (eta' or G') of the "pure" resins or blends. It is suggested that the molecular order [see Hussein and Williams, J. Non-Newt. Fluid Mech, 86. 105 [1999]: Hussein and Williams, Macromol Rapid Commun, Is. 323 (1998)] and mismatch of the molecular conformations of different polyethylene structures provide an explanation for the immiscibility of polyethylenes. Agreement was observed between the measured dynamic properties and theoretical predictions of Palierne and Bousmina-Kerner emulsion models.