Ultrasonographic biometry was performed in 56 patients immediately after implantation of a posterior chamber intraocular lens to measure the position of the lens. A modified applanation method was used to avoid injury to the scleral suture. Ten months later, 44 of these patients were examined by the same method. The anterior chamber depth was found to have decreased from 4.26 mm (s = 0.39 mm) in the immediate postoperative period to 4.2 mm ten months later. However, axial length, at 23.28 mm postoperatively and 23.34 mm at follow-up, and mean corneal refraction (43.28 D and 43.34 D, respectively) were practically unchanged. There was a shift in the spheric equivalent of refraction from postoperative emmetropia (mean -0.07 D) to slight myopia (mean -0.76 D) at follow-up. This mean myopization of 0.69 D corresponded to the tendency toward a shallower anterior chamber. Shrinkage and fibrosis of the posterior capsule, reduced elasticity of the polypropylene loops, flattening of the cornea and axial changes are discussed as possible causes. The tendency toward myopization should be taken into account when calculating the power of sulcus-fixated posterior chamber lenses.