The anatomy and biomechanics of the acromioclavicular (AC) joint have been understood for a long time; however, the importance of this joint in the clinical setting is often underestimated. During clinical examination various sensitive functional tests can document any AC pathology. For X-ray documentation special techniques are necessary. Other imaging techniques are rarely indicated. The Rockwood classification for AC joint separation has increased our understanding of the pathology, which, in turn, leads to a better understanding of conservative and surgical therapy. Within the last few decades surgical treatment has shifted from AC to coracoclavicular stabilization. In patients with clinically relevant degenerative joint disease, resection of the lateral clavicle has proved to be a reproducible procedure. This operation can be performed using the conventional, open technique or with a minimally invasive procedure (arthroscopic resection of the AC joint; ARAC). In unstable joints, resection should be combined with a stabilization procedure.