Degenerative ossification is formed directly at the major tubercle. Like in any other gliding tendon, fibrocartilage cells lie on the articular side of the rotator tendon at the pivot of the humerus head. Typically, the calcific deposits of calcifying tendinitis are found between these two areas. At this site, hydroxyapatite is usually formed by fibrocartilage cells through an unknown stimulus. There is no ossification. This is a two-phase disease. During the chronic initial phase, a calcific deposit is formed in the tendon of the rotator cuff. In the X-ray, it is clearly circumscribed and has a dense appearance (type I). Pain is inconsistent and may exist for years. In the acute phase, the deposit undergoes spontaneous resolution. Now it takes on a translucent and cloudy appearance without clear circumscription (type III). Patients experience severe pain for 2-3 weeks. Finally, a normally functioning shoulder joint will result. The X-ray therefore allows a prognostic conclusion. In a study including 235 calcific deposits, it became clear that there are some cases where it is not possible to designate the specific X-ray morphology to a given deposit (type II). Irrespective of the phase of disease, the so-called calcific deposit is composed of poorly mineralized hydroxyapatite. For a diagnosis, we require: a typical history, clinical findings consistent with tendinitis of the rotator cuff, calcific deposits in the tendon associated with signs and symptoms of tendinitis. It is recommended that radiographs be taken at least in AP projections with the shoulder in internal and external rotation to demonstrate the deposits without super-imposition. Ultrasound shows concomitant bursitis and is useful for the differential diagnosis of rupture of the rotator cuff. Radiographic diagnosis is most difficult when there are small opacifications near the rotator attachment. In this case, allocation may become possible only later in the course of disease. Initial treatment should always be non-operative. Almost all therapeutic modalities are said to be quite successful. Needles under local anesthesia is recommended only for patients with marked pain who lack any signs of resolution in the X-ray. According to a prospective study, the success rates of needles depend on the roentgenologic findings: in type I deposits, resolution occurs in 33%, in typq II deposits in 71%. Freedom from pain is seen in about 50% of the patients. Type III deposits undergo resolution with and without therapy in about 2-3 weeks. Post-operative results are reported to lie between 77% and 96% irrespective of the method used.(ABSTRACT TRUNCATED AT 400 WORDS)