The aim of the present study was to investigate the mRNA expression of several cytokines which were not reported previously from interface tissues around loose cemented acetabulum to obtain better understanding of the biological mechanisms connected with aseptic loosening and osteolysis of THA. We investigated mRNA expression for several cytokines (interleukin-1 alpha [IL-l~a], IL-lp, IL-2, IL-2 receptor[2R], IL-4, IL-5, IL-8, IL-10, transforming growth factor-beta [TGF-p], and interferon- gamma [IFN-y]) by reverse transcription-polymerase chain reaction (RT-PCR) and release of metalloproteinase (MMP)-2 and MMP-9 from the cement-bone interface tissues around five loose polyethylene acetabular components. We did not include TNF-a and IL-6 because the biologic effect of the former is so similar to that of IL-1, and the latter fails to stimulate prostaglandin E, or collagenase production by fibroblsts or synovial cells. Expression of mRNA for IL-1p was detected in four, IL-2R and IL-8 in three, IL-10 and TGF-p in two of five interface tissues .No expression of mRNA for IL-la, IL-2, IL-4, IL-5, and IFN-p was detected. Zymographic analysis for gelatinase/type IV collagenase revealed gelatinolytic bands corresponding to metalloproteinase(MMP)-2 and MMP-9 in cemenl-bone interface tissues. Activated cells phagocytose particles in cement-bone interface tissues expressed more cytokines mRNA than previously known to be related to periprosthetic bone resorption, and secreted metalloproteinases associated with extracellular matrix degradation and fibrosis.