The coarsening rates of the two-phase morphologies of linear polyethylene/poly(ethylene-co-1-octene) blends were determined as functions of molecular weight. Samples with cocontinuous morphologies that were prepared through solution blending were annealed in the melt state for various times, and subsequently the length scales of the morphologies were determined with a line-intersection method. Length-scale data were multiplied by a function that normalized for the effects of differences in zero-shear-rate viscosity and thermal energy; after normalization, the data largely fell on one trend line within the bounds of experimental error. This indicated that the principal effect of increasing molecular weight was to slow the coarsening rate through an increase in melt viscosity, with little effect from the thermodynamic compatibility of the two polymers. (C) 2003 Wiley Periodicals, Inc.