[en] Biocompatibility and preliminary toxicity of a novel gentamicin-loaded monoolein gel (implant) intended for the local treatment of chronic osteomyelitis were investigated in mice. The mice, randomly allotted in 3 groups of 10, received respectively a single dose (0.05 mL) of normal saline, monoolein and the gel by subplantar injection. Clinical monitoring and assessment of induced oedema were carried out during 52 days after implantation. A histologic examination of the implantation site was performed at the end of the experiment. Renal and hepatic functions of the implant were also assessed on 52 days post-implantation by using biochemical and histological methods. In mice, no adverse reaction occurred after implantation. Only, a transitional foreign body reaction was observed in mice implanted by the monoolein and the implant. The paw volume of the mice increased within 3 h post-implantation and returned to baseline by 52 days. The liver and kidneys histology at light microscopy and biochemical parameters were similar for all mice. Further investigation is undertaken to detect eventual early damages which could have been resolved with time. Nevertheless, the novel gel is biocompatible and doesn`t show sub-chronic toxicity.