This case control study compared the nasolacrimal duct (NLD) patency in a random sample of phacoemulsification cataract surgery patients (control group) versus a consecutive series of patients who developed endophthalmitis post cataract surgery (case group). NLD syringing was performed in both groups of patients. If the NLD was not patent on syringing, then a macro-dacryocystogram (MDCG) was performed. In the control group 11.8% (4/34 eyes) had NLD obstruction on syringing vs. 50% (5/10 eyes) in the endophthalmitis group (P=0.018). The rate of radiologically confirmed NLD obstruction on MDCG was lower at 2.9% in the control group vs. 20% in the endophthalmitis group (P=0.125). The authors conclude that NLD obstruction is a significant risk factor for postoperative endophthalmitis, therefore screening for symptoms and examination of the lacrimal system prior to cataract surgery is recommended.