We describe a model which can be used for in vitro biocompatibility assays of biomaterials. We studied the in vitro response of human osteoarthritis or rheumatoid arthritis fibroblast-like synoviocytes to Al. 2. O. 3. or ZrO. 2. particles by analyzing the production of interleukin-1 (IL-1) and interleukin-6 (IL-6) and the metabolism of arachidonic acid via lipoxygenase and cyclo-oxygenase pathways. Our results show that, in these cells and under our experimental conditions, Al. 2. O. 3. and ZrO. 2. did not significantly modify the synthesis of IL-1 and IL-6 or the metabolism of arachidonic acid