To evaluate the clinical value in diagnosis and treatment of lens subluxation using ultrasound biomicroscopy (UBM). This study comprised 29 patients (32 eyes) that had cataract with subluxated lenses due to different causes admitted into our hospital between November 2000 and January 2002. All eyes received UBM examination preoperatively and postoperatively. Capsular tension ring (CTR) implantations were performed using different technique according to UBM examination. Then all patients received phacoemulsification and intraocular lens (IOL) implantation. The location of IOL and CTR and complications were evaluated postoperatively. Different kinds of subluxated lens shown different manifestations in UBM. The degree of zonular defect can be evaluated with UBM preoperatively. With UBM examination preoperatively, extent of lens subluxation less than 1/2 quadrant in 19 eyes while more than 1/2 quadrant in other 13 eyes were observed. Postoperative UBM examination in this series shown that CTRs were holding in pla