To determine the current bacteriology of lacrimal duct obstruction (LDO) and to relate the bacteriological findings to the type of symptoms.127 samples were obtained from the lacrimal sac in 118 consecutive adult patients with LDO, including nine bilateral cases.Altogether, 156 isolates were recovered from the 127 samples cultured. Cultures were positive from 84% of the samples. Gram positive bacteria were isolated in 79 (62%) samples. The most frequently cultured bacterial species was Staphylococcus epidermidis, representing 27% of the isolates. Gram negative bacteria were recovered from 26 (20%) samples, and these bacteria were statistically significantly more common in cases with copious discharge than in cases with minor discharge (p = 0.000). Cases with simple stenosis of the lacrimal duct (SSLD) showed significantly less Streptococcus sp (p = 0.004) and Gram negative organisms (p = 0.004) than those with chronic dacryocystitis.The bacteriology of SSLD resembles that of normal conjunctival flora. Chronic dacryocystitis in adults is associated with an increased proportion of Gram negative bacteria which may be a reservoir for postoperative intraocular infection. They should also be taken into account in selecting antimicrobial prophylaxis in lacrimal drainage surgery.