OBJECTIVE To identify risk factors for intraoperative vitreous complications in resident-performed phacoemulsification surgery. METHODS Two urban public county hospitals. METHODS Case series. METHODS Phacoemulsification cataract surgeries performed by residents between January 4, 2005, and January 8, 2008, were retrospectively reviewed. Clinical characteristics of patients with and without intraoperative vitreous complications were compared and independent factors associated with vitreous complications identified using univariate and multivariate analysis. RESULTS Of 2434 cases meeting inclusion criteria, there were 92 vitreous complications (3.8%). On univariate analysis, significant preoperative risk factors for vitreous complications included older age (P=.020), poor preoperative corrected distance visual acuity (CDVA) (P=.007), left eye (P=.043), history of trauma (P=.045), prior pars plana vitrectomy (P=.034), dementia (P=.020), phacodonesis (P=.014), zonule dehiscence (P<.0001), posterior polar cataract (P=.037), white/mature cataract (P=.005), dense nuclear sclerotic cataract (P=.0006), and poor red reflex (P=.002). Factors that remained significant on multivariate analysis were older age (odds ratio [OR], 1.03; 95% confidence interval [CI], 1.01-1.05), poor preoperative CDVA (OR, 1.52; 95% CI, 1.14-2.03), left eye (OR, 1.63; 95% CI, 1.05-2.51), prior pars plana vitrectomy (OR, 1.88; 95% CI, 1.01-3.51), dementia (OR, 3.65; 95% CI, 1.20-11.17), and zonule dehiscence (OR, 8.55; 95% CI, 3.92-18.63). CONCLUSIONS Elements of the preoperative history and examination can identify patients at higher risk for intraoperative complications during resident-performed phacoemulsification surgery.