Introduction: Rapidly destructive arthrosis of the hip (RDHD) is a rare and incompletely understood disorder with scarce literature about variations in natural history within a population. A series of cases from North Wales with rapid progressive joint destruction and extensive subchondral bone loss in the femoral head and acetabulum are presented. Methods: A retrospective review of patients with a clinical profile and serial radiographs suggestive of a rapidly progressive hip disease was undertaken. This revealed 15 patients who met our criteria for RDHD. A retrospective analysis of clinical and radiographic records was performed. Radiographic findings mimicked those of other disorders such as septic arthritis, rheumatoid and seronegative arthritis, primary osteonecrosis with secondary osteoarthritis, or neuropathic osteoarthropathy, but none of the patients had clinical, pathologic, or laboratory evidence of these entities. Results: Rapid progression of hip pain and disability was a consistent clinical feature. The average duration of symptoms was 1.4 years. Radiographs obtained at various intervals before surgery (average 14 months) in 15 patients documented rapid hip destruction, involvement being unilateral in 10 cases. All patients underwent total hip arthroplasty, and osteoarthritis was confirmed at pathologic examination. Histology of femoral heads failed to show the findings typical of primary osteonecrosis & no evidence of sepsis. Discussion: The authors postulate that these cases represent an uncommon subset of osteoarthritis and regular review, both clinically and radiologically, are required to assess speed of progression and prevent rapid loss of bone stock without the surgeon being aware. These cases are unsuitable for being placed on long waiting list due to technical difficulties in delayed surgery and compromised outcome following surgery. The decisions about the need for surgery and the selection of cases should be made purely on clinical grounds and not on their rank in the waiting lists.(295)