We observed early failure and radiographic signs of accelerated wear as early as one to three years after insertion, without cement, of a metal-backed acetabular component with a liner made of Hylamer (DePuy). This finding prompted us to review a larger cohort of patients in whom that liner had been used. Two hundred and thirty-three components with a Hylamer liner, evaluated at a minimum of two years, had a mean rate of wear of 0.27 millimeter per year compared with 0.12 millimeter per year for a contemporaneous group of fifty acetabular cups with a conventional ultra-high molecular weight polyethylene liner made by another manufacturer.At a mean of 3.2 years, we found a significant difference (p < 0.000000006) between the mean rate of wear (0.20 millimeter per year) when the Hylamer liner articulated with a DePuy modular cobalt-chromium femoral head and the mean rate (0.29 millimeter per year) when the liner articulated with an Osteonics modular cobalt-chromium femoral head. Radiographic evaluation revealed a significant correlation between the total linear wear and the prevalence of osteolytic lesions (r2 = 0.76, linear regression analysis). We found that wear of 1.5 millimeters or more could be detected by the unaided eye. Because of the positive correlation between osteolysis and wear of 1.5 millimeters or more, we defined a hip with a liner that had that amount of wear as a hip at risk.We concluded that the wear characteristics of a Hylamer liner in vivo are inferior to those of a conventional ultra-high molecular weight polyethylene liner. Also, the rate of wear of the liner is greater when the femoral head is from a manufacturer other than DePuy. A patient who has a total hip replacement that includes a Hylamer liner should be monitored frequently for signs of wear and osteolytic changes. Additional investigations, with longer durations of follow-up and larger populations, are needed to understand fully the importance of our findings.