The manubriosternal joint has been a matter of histological and anatomical discussion due to diversity of clasifications. It has been described as sinfisis, cartilagonous primary joint, synchondrosis or as a synovial joint. The objetive of this study was to determine the type of tissue that from this structure. Sternons were obtained from 10 chilean male cadavers ( 7 fresh and 3 formalized), 40 to 60 years old. The manubriosternal joint was examined macro and microscopally. Each joint was identified and the manubriosternal joint was examined sectioning the bone 1 cm above and 1 cm below the inter articular line. The segments were descalcified and 9 pieces were obtained in anteroposterior sections: 3 from the median part of the joint and 3 from each lateral proximal part of the sternocostal joint. The samples were stained with hematoxiline-eosin stain and van Giesson. The histologic examination determined, that in 5 cases (50%) the was a fine periferic layer of hialinic tissue. This tissue covered the surfaces articulars of the manubrium and sternal body. It was also found, between both surfaces a moderate (+++) fibrocartilaginous tissue in 3 cases (30%) was found a hialinic tissue between the articulars surfaces and abound fibrocartilaginosus tissue (+++) and in 2 cases (20%), the cartilaginosus tissues thar covered the articulars surfaces was abound with minimum fibrocartilaginous (++) in the central region. In 6 cases (60%) there was a small cavity in the fibrocartilaginous. The manubriosternal joint presented their surfaces covered with cartilaginosus tissue of hialinic type in relation with fibrocartilaginous tissue. This last tissue was a real disc between the articulars surface. In the majority of the cases was found a small cavity, perhaps due to the absortion that its central part suffers this loock more like a synovial joint than a synchondrosis. This could be due to a periferic calcification or to a sinostosis manubriosternal. In conclusion, this joint could be defined as a sinfisis. This reminded an old clasification that defined it as "diartroanfiartrosis", a transition joint between the synovial articulations and cartilaginosus