Pseudomonas osteomyelitis was produced in forty-seven rabbits by the injection of sodium morrhuate and Pseudomonas aeruginosa into the tibial marrow cavity. Sisomicin (4-5 dehydro-gentamicin) and carbenicillin were administered alone and in combination. The disease process was evaluated by observation, leukocyte counts, roentgenograms, and at death by gross pathology and bone cultures. Treatment begun on the day of infection markedly inhibited the development of disease. Three weeks of therapy were required to sterilize the infected bone regardless of the time of initiation of treatment. The combination of carbenicillin and sisomicin was significantly more effective than either drug alone in producing a bacteriological cure and preventing sequestrum formation.