Aims: A prospective multicentric study was carried out in patients having metal-on-metal METASUL components to check if the concentration markers of chromosomal damage (Sister Chromatid Exchanges (SCEñs) and Micronuclei (Mni) and that of Co, Cr, Ni and Mb in the body ßuids are affected by the implant of METASUL components within 6 months. Methods: 30 patients were enrolled homogeneous as to the exposition to mutagenic agents. Observation times were pre-op., 7 days, 2 months, 6 months; blood and urine samples were taken at each observation time, and the markers of chromosomal damage (blood) and the ion concentration (blood and urine) were measured. Results: measurements showed a 2-fold increase of Co in blood, a 10-fold increase of Co in urine, a 1.5-fold increase of Cr in the blood and a 3-fold increase of Cr in the urine at a follow-up of 6 months from the operation; the Ni blood concentration was also increased at the 7 day check-up. The study cohort did not show any modiþcation in the frequency of markers of chromosomal damage at any of the observation times. The amount of the SCEñs and Mni recorded at all the observation times did non correlate with each other nor with any of the ion levels measured in the blood and in the urine. Conclusions: the implant of prostheses with METASUL components determines an increase in the concentrations of mainly Co and Cr in blood and urine, but that this increase has no genotoxic effects on the peripheral lymphocytes in the selected group at a follow-up of 6 months.