The authors report three observations of osseous and/or articular actinomycosis. Osseous localizations, always in contact with abscessed foci of the soft tissues, included the spine and one or several limbs. In one case there was an arthritis of the knee. Culture and typing of the responsible germ: Actinomyces meyeri, were obtained from infectious foci in the three cases. The authors insist on the rare occurrence, at the moment, of osteo-articular actinomycoses outside the maxillo-facial area. Actinomyces meyeri has exceptionally been implicated. The prognosis of osteo-arthritis is similar to that of other localizations. It is usually favorable due to the great sensitivity of the germs to antibiotics, especially penicillin.