A prospective study has been made of 49 patients with the frozen shoulder syndrome (as distinct from tendinitis, calcific deposits and frozen shoulders occurring after coronary infarction or with pulmonary tuberculosis) of whom forty-one have been followed up for 5-10 years, always to their greatest recovery. There were three consecutive stages: pain, stiffness, and recovery. The stiffness stage was usually related to the duration of the recovery stage. The total duration was longer than is generally supposed (an average total of 30.1 months in contrast to about 18 months as often postulated). Generally speaking, the longer the stiffness stage is, the longer is the recovery stage. In 4 patients the second shoulder became similarly affected, 6 months to 7 years after the first, and followed a similar chronological sequence to the first. After greatest recovery, slight restriction of movement was found in more than half the cases, but in only 3, all of long duration, was the restriction a handicap. Arthrography, carried out on both shoulders in all patients during the recovery stage, showed in the affected shoulder fewer rotator cuff defects than expected at this age and fewer (four) than in the contralateral one (twenty-three); seemingly, the condition leads to the obliteration of some defects.