To investigate the duration and pattern of cataract formation after pars plana vitrectomy, thirty-three eyes from 33 patients with complete data from March 1995 to January 2000 were collected in this study. The time and pattern of cataract formation was analyzed according to Lens Opacities Classification System III (LOCS III). The correlation between the mean cataract progression and follow-up time was determined by simple regression and correlation analysis. Diabetes mellitus and hypertension were the main causes of patients with vitreoretinopathy who underwent pars plana vitrectomy procedure. Twenty-one patients (63.6%) had diabetes mellitus and 11 patients (33.3%) had hypertension. Four eyes (13.8%) received intravitreal gas injection after pars plana vitrectomy. The correlation between cataract progression and follow-up time was clinically significant (p < 0.05). Thirty-one patients (94%) were nuclear cataract, the mean time of cataract formation being 9.1 months; 15 patients (46.9%) were cortical cataract, the mean time of formation being 8 months; and 24 patients (72.7%) were posterior subcapsular cataract, the mean time of formation being 13.3 months. Cataract formation after pars plana vitrectomy is not infrequent. Nuclear cataract is the most common type in this study. Vitreous microenvironmental changes, post-vitrectomy uveitis, intravitreal gas, and patient age may be the key points of cataract formation after surgery. The mechanism of longer-term effect of pars plana vitrectomy on lens status is still unknown and merits further study.