Four cases of an uncommon congenital skeletal anomaly, isolated bilateral glenoid hypoplasia, are presented with discussion of the possible pathogenesis and clinical significance. Bilateral computed tomographic arthrography of the shoulder demonstrated thickening of the inferior glenoid cartilage in two cases. The technique was of value in the symptomatic shoulder revealing the location of a contrast medium filled cleft within the posterior cartilage in one case and the true configuration of the glenohumeral joint in the second case, when the degree of deformity had rendered plain radiographs and conventional arthrography uninterpretable.