A high density polyethylene homopolymer was blended with a linear low density ethylene hexene copolymer over the composition range of 0-100%. The resistance to slow crack growth was measured by a notched tensile test under constant load at 42, 60 and 80-degrees-C. The morphology was varied by slow cooling, quenching and annealing at 129-degrees-C for 24 h. Whereas the resistance to slow crack growth increased by a factor of 10(6) over the composition range, the differences in morphology could only change the resistance to slow crack growth at the most by a factor of approximately 3. The effect of temperature was independent of the effect of composition on slow crack growth. The effects of molecular and morphological structure are discussed.