Thirty-four patients (thirty-eight hips) had a primary total hip arthroplasty with insertion of a non-porous-coated titanium-alloy acetabular component without cement. This component is initially stabilized with use of a central acetabular polyethylene peg, which is inserted into the pelvis, as well as supplementary cortical-bone screws inserted into the ilium. The original diagnosis was degenerative joint disease in thirty-four hips and avascular necrosis in four hips. Twenty-five femoral components were inserted with cement, and thirteen non-porous-coated femoral implants were inserted without cement. The acetabulum was prepared with so-called line-to-line reaming. Thirty-five hips in thirty-one patients were available for clinical and radiographic follow-up at a mean of 4.5 years (range, two to seven years). Serial measurements of the position of the acetabular component revealed that eighteen cups (51 per cent) had migrated. Of these, eleven had been revised. Radiolucent lines of at least one millimeter in thickness at the bone-prosthesis interface were noted adjacent to all but six of the acetabular components. Although this series was small, it demonstrates an unacceptably high rate of failure of non-porous-coated acetabular components after a relatively short duration. We question the efficacy of this acetabular component, inserted without cement, as part of a primary total hip arthroplasty.