Using low and constant-impact energy, a relatively simple method of impact fatigue has been devised to provide toughness measurements on polymers. Crystalline polymers, particularly the nylons and polyacetal, appear to have better fatigue performance than noncrystalline polymers. Fatigue curves that are normalized with the fracture area can potentially detect the influence of crystalline morphology on fatigue. Using retained energy values and fracture area measurements from each impact, an estimate of the fracture energy is obtained. The higher fracture energy values obtained in fatigue, over those obtained in single-blow impacts, indicate that different energy absorption processes occur in single- and multiple-impact testing.