A biodegradable drug delivery system of a gentamicin loaded chitosan bar with sustained antibiotic effect is described. Chitosan has proven to be a biocompatible aminopolysaccharide and a matrix for controlled release of pharmaceuticals. Combined crosslinking, solvent evaporation, and a cylinder model cutting technique was used to prepare the chitosan bar. Sustained diffusion of gentamicin into the surrounding medium was seen using a release test in vitro. Approximately 11% gentamicin was released from the bar in the first 24 hours. The gentamicin released from the bar showed significant antibacterial activity. The bar implanted in the proximal portion of the rabbit tibia produced a low blood concentration of gentamicin, but a much higher concentration was produced in local bone and in the hematoma. In all bone tissue around the bar, the gentamicin concentration exceeded the minimum inhibitory concentration for the common causative organisms of osteomyelitis for approximately 8 weeks. The implant caused no systemic side effects. Based on these test results together with the chitosan characteristics of biodegradable, antibiotic, and immunologic activity, the gentamicin loaded chitosan bar seems to be a clinically useful method for the treatment of bone infection. This system has an advantage over other systems in that it avoids a second operation for removal of the carrier.