The tear energy (G(c)) of high-density polyethylene (HDPE) and HDPE/ethylene copolymer blended drawn tapes in orientation direction has been studied systematically with respect to structural parameters. In all cases the values of G(c) were in the range of 0.8-8.0 kJ m(-2). The results showed a direct relationship between amorphous phase orientation and G(c) of drawn tapes. The decrease in G(c) with molecular orientation of tapes is due to the formation of large number of elongated voids at the interfibrillar regions and diminution of viscous flow occuring in the vicinity of the propagating crack tip. An increase in G(c) in the range of 15-45% was obtained for HDPE blended tapes containing about 10% of the second-blend component either as ethylene-vinyl acetate or ethylene propylene-diene terpolymer or ethylene-propylene block copolymer. This relates to the increase in fraction of amorphous phase and extensive molecular network in the interfibrillar amorphous regions.