Acetabular replacement without cement using three types of pegged polyethylene prostheses was begun as a prospective trial by Morscher (August 1977). Ring (June 1979), and Freeman (January 1980); 1878 hips have been replaced using this technique and are reviewed. Follow-up averaged 2 years (range: 6 months-6 years). Successful pain relief and satisfactory walking ability were present in 97% and adequate flexion in 90%. Radiographic review showed the consistent development of a stable, uniform sclerotic line adjacent to the prosthesis. No component migration could be documented. Ten hips have been revised for obvious femoral loosening, and two acetabula showed slight motion during revision for femoral failure and were revised. Deep infection (0.37%) occurred only in patients not receiving perioperative antibiotics and not operated upon in unidirectional filtered air-flow enclosures. Postmortem histological evaluation of eight hips showed a thin fibrous membrane separating the prosthesis from viable bone. These results are preliminary, but nevertheless at least as good as those in any large series of cemented acetabula with the same follow-up. The advantages of this technique are its reproducible results, low complication rate, limited invasion of the skeleton, and easy revision should failure occur.