The increasing use of plastics as strong, load-bearing materials in industry has raised certain questions about the standard tests used to describe their performance. Even after all of these tests have been run, there are still several unanswered questions. How will the fabricated part stand up under impacts in service? What kind of melt flow can be expected in the normal injection molding process? Will increasing glass content improve stress crack resistance? What is the effect of fiber orientation on material properties?These are the questions that this paper attempts to deal with in terms of “Alathon”* glass-fiber reinforced, high density polyethylene. Because they represent difficult areas of interpretation, they are in need of more attention. Other standard test results on Du Pont’s family of glass-reinforced, high density polyethylene resins are also presented.