Members of the genus Enterobacter are commensal organisms of the gastrointestinal tract and are considered pathogenic only for patients with lowered resistance to infection (e.g., chronic infection, cancer, or diabetes mellitus) or those with impaired immunity (congenital, acquired, or impaired immunity secondary to therapy). We report on four cases of endophthalmitis caused by Enterobacter cloacae: two in patients with acute postoperative endophthalmitis, one in a patient with delayed bleb-related endophthalmitis, and one in a patient presenting with presumed posttraumatic endophthalmitis. Each patient presented with severe disease many days after the onset of ocular symptoms, and two patients had systemic risk factors accounting for a reduced resistance to infection. Endophthalmitis caused by gram-negative bacilli is characterized by acute onset, rapid progression, and poor final visual outcome. Each of these patients was treated by a standard protocol with intravitreal, systemic, and topical antibiotics and systemic steroids. Despite treatment, the final visual outcomes for three of these patients was no perception of light, and that for one patient remained perception of hand movements only. In common with endophthalmitis caused by other gram-negative organisms, intraocular infection secondary to Enterobacter cloacae infection is a devastating disease which, despite treatment, results in extensive ocular damage and severe visual loss. Since 1966, only four cases of endophthalmitis secondary to infection with members of this genus have been reported. This report presents four cases which occurred over a period of 14 months and, to the best of our knowledge, the first case of bleb-related endophthalmitis secondary to E. cloacae infection.