Aims: The aim of the study was to investigate the anatomy of the medial collateral ligament of the Articulatio cubiti and to analyse its clinical importance. Methods: Eight alcohol-formalin-glycerol þxed elbow joints were dissected (age range 65 Ð 78). The muscles of the arm, elbow and the forearm were removed. The ligaments of the elbow joint were þnely dissected. The joint cavity was opened and the intra-articular anatomy of the medial collateral ligament was described. Results: In all the investigated specimens the Lig. collaterale ulnare was composed of three parts Ð Partes anterior, posterior et obliquus. The oblique (transverse) part of the ligament spread between Processus coronoideus and Olecranon. Intra-articularly the Pars obliqua strengthened the joint capsule at the lower part of the ulnohumeral connection in all the dissected specimens. Conclusions: It is the common belief, that the oblique part of the Lig. collaterale ulnare is unstable anatomical variation, that does not cross the ulnohumeral joint. According to our þndings it is a constant anatomical structure that is intra-articularly visible within the lower part of the medial joint capsule. It does not connect only the bony parts of the Processus coronoideus and Olecranon, but also strengthens the articular joint capsule and contributes to elbow stability. This anatomical fact should be taken into consideration during the diagnosis and treatment of different elbow joint pathologies.