We obtained postoperative blood concentrations of Co, Cr, Mo, Ti, Al and Nb in 75 patients undergoing primary THA at our institution between January 1998 and December 2000. All patients were treated with the same prosthetic device (Alloclassic VARIALLTM, Zimmer, Winterthur, Switzerland) using three types of articulations: metal-on-metal (METASULTM ), ceramic-on-ceramic (CERASULTM) and metal-on-cross linked polyethylene (DURASULTM). 25 patients out of each articulation-group were evaluated by blood analysis 24-38 months after surgery. The patients were submitted to strict criteria of inclusion. Comparing the three articulation-groups there were no significant differences in the categories age, follow-up time and preoperative blood level of creatinine. The Al-, Ti- and Nb-blood levels were all below their detection limit. Regarding the median blood concentrations of Mo, we found no statistically significant differences comparing the three articulations (p>0.05). The median Co blood concentration in the ceramic group was 0.19 ng/mL, 0.69 ng/mL in the metal group and 0.19 ng/mL in the cross-linked PE group. The difference between the metal and ceramic group and between the metal and polyethylene group is statistically significant (p=0.001 in both comparisons). The median blood concentration of Cr was 0.19 ng/mL in the ceramic and in the cross-linked PE group, and 0.47 ng/mL in the metal group, the difference being statistically significant (p=0.003 and p=0.0002). Although the blood concentrations of Co and Cr were significantly higher in patients with a metal-on-metal articulation they were far from reaching toxic levels. (Hip International 2005; 15: 136-42).