Soft tissue necrobiosis and T-lymphocyte infiltration within the periprosthetic soft tissue have been linked to a suggested hypersensitivity reaction of the delayed-type following the metal-on-metal arthroplasty. While we observed both synovial necrobiosis and lymphocyte infiltrates in synovial tissues with failed metal-on-polyethylene prostheses, we hypothesized that both findings are unspecific for metal-on-metal bearing coupes. Thus, we wished to quantify the extent of necrobiosis and the amount of T-lymphocyte infiltration in aseptically loosened metal-on-polyethylene prostheses.