The influences of molecular weight and m-LLDPE comonomer type on the miscibility of m-LLDPE with LDPE in the melt state were investigated with theological methods. Dynamic, steady shear and transient measurements were carried out in an ARES rheometer at 190 degreesC. The M, of the shortly branched m-LLDPE has influenced its miscibility with LDPE and immiscibility has increased with the increase in M. of m-LLDPE. The miscibility of the high-M-W m-LLDPE with LDPE was non-symmetric with respect to composition as revealed by the dependence of their eta(0), eta(1) (omega), G(1), N-1 (gamma), N-1 (t) on blend composition. Addition of a small amount of the hexene m-LLDPE to LDPE was more likely to cause immiscibility than the addition of a small amount of LDPE to m-LLDPE. Increasing the m-LLDPE branch length (comonomer) from butene to hexene did not influence the miscibility of m-LLDPE/LDPE blends. Agreement was observed between the measured theology and theoretical predictions of Einstein, Scholz et al., Palierne and Bousmina emulsion models. The ratio of interfacial tension to droplet radius was estimated to be similar to10(3) N/m(2).