A biodegradable implant containing gentamicin sulphate for the prevention orr the treatment of bone infections was designed by using, as the polymer material, sodium alginate containing a high proportion of mannuronic sequences capable of forming a complex with the drug. By a crosslinking procedure with calcium ions, insoluble but biodegradable calcium alginate spheres were obtained and formed into a chain by means a surgical wire. To evaluate the implant effectiveness, the implant was inserted at the femur level of Wistar rats and gentamicin levels in plasma, bone and soft tissues were detected by microbiological assay. The gentamicin concentrations were found to be sufficiently high to control pathogens for at least 30 and 7 days in the bone and soft tissue, respectively, whereas plasma levels were low and detectable for only 1 day. The complete implant bioabsorption occurred within 8-10 days after implantation and no signs of rejection or inflammatory reactions were observed at the level of the surrounding tissues.