The iris in Williams syndrome. Forty three children with Williams syndrome and 124 control subjects had their eyes photographed. The photographs were examined by three ophthalmologists and four geneticists of varying experience. A stellate pattern was noted more often in the irides of patients with Williams syndrome (51%) than in those of the control subjects (12%), and was more difficult to detect, or was absent, in heavily pigmented irides. We conclude that the stellate pattern is of diagnostic importance, particularly if the pattern is carefully defined and the clinician is experienced. 