We reviewed 12 patients with primary glenoid dysplasia. Ten were assessed clinically and two from case notes and radiographs. We identified two groups according to the age at onset of symptoms. The first (seven patients) consisted of boys and younger men, all of whom developed symptoms before the age of 40 years. All four children were free from pain, whereas the three adults in this group had varying degrees of this. Four patients had symptoms of instability. The second group consisted of older men (five patients) all of whom had noted the onset of symptoms, in the form of pain and stiffness, after the age of 40 years. All five had radiological evidence of osteoarthritis. Although the four children in our study had minimal symptoms, all eight adults had ongoing shoulder pain and dysfunction, despite a specific rehabilitation programme. Four patients required surgery; one had posterior stabilisation for instability and three arthroplasties of the shoulder for osteoarthritis