Purpose: To evaluate the position of the iris insertion into the ciliary body in persons with pigment dispersion syndrome (PDS) and control subjects. Methods: Ultrasound biomicroscopy was performed on 19 eyes with PDS and on 21 eyes of control subjects. A radial, perpendicular image in the temporal meridian detailing Schwalbe line (SL), scleral spur (SS), and iris root insertion (IR) was obtained for each eye by a single examiner. The distances between these structures then was measured. Results: There were no differences between the groups in refractive error (mean ± standard error, - 2.8 ± 0.7 diopters for PDS eyes versus -2.2 ± 0.6 for control subjects) (P = 0.46), sex distribution (P = 0.49), and trabecular meshwork height (SL to SS) (0.63 ± 0.03 mm [PDS eyes] versus 0.59 ± 0.03 [control eyes]; P = 0.24). The SS-to-IR distance was significantly greater in PDS eyes (0.40 ± 0.04 mm) than in control eyes (0.28 ± 0.04 mm) (P = 0.01) as was the overall distance from SL to IR (0.98 ± 0.04 mm versus 0.81 ± 0.04 mm) (P = 0.003). Conclusion: The insertion of the iris into the ciliary body is more posterior in PDS eyes than in control eyes. This anatomic variation places the iris pigment epithelium proximal to the zonular apparatus and may increase the likelihood of iridozonular contact and zonular pigment dispersion.