A radiographic study was done of 171 total hip replacements that had been followed for an average of 3.3 years (range, two to five years). The study was performed to assess the incidence of loosening of the femoral component in older adult patients (average age, sixty years) in whom the medullary canal had been plugged with methylmethacrylate (using the medullary plug syringe to introduce the plug) prior to introducing the cement (Simplex P) with a cement-gun. Most of the femoral components that were used were of the CAD or HD-2 design, and all were made of chromium-cobalt alloy. Three categories of loosening were defined: definite (requiring radiographic evidence of migration of the component or the cement), probable (requiring evidence of complete 100 per cent radiolucent zone around the cement mantle on one or more radiographs), and possible (requiring evidence of a radiolucent zone that occupied more than 50 but less than 100 per cent of the cement-bone interface on one or more radiographs). One hip required revision for a loose femoral component and another patient had asymptomatic subsidence of the femoral component. Thus, the total incidence of definitely loose femoral components was 1.1 per cent. No hip was classified as having probable loosening; seven hips (4 per cent) were rated as having possible loosening. Compared with the results of four other published reports of patients of similar age with similar follow-up, and using the same radiographic criterion for loosening, the current series demonstrated a statistically significant reduction in the incidence of definitely loose femoral components.