The blown films of high-density polyethylenes with unimodal and bimodal molecular weight distribution were prepared under several processing conditions, and their morphologies were extensively characterized. The high molecular weight tail (MW > similar to 10(6)) of the molecular weight distribution seems to play a critical role on the morphology of blown high density polyethylene films irrespective of the molecular weight distribution mode of the resins. As the content of high molecular weight species increased, the tendency for high stress-crystallization increased and the network structure of lamellar stacks was better developed. The intercrystalline connectivity along the normal direction of lamellar stacks was higher than that along the transverse direction of lamellar stacks.