In a consecutive series of 710 cataract extractions, unintentional postoperative filtering blebs occurred in 18 eyes. The incidence of filtering blebs after limbus based conjunctival flaps vs after fornix based conjunctival flaps was 7:1. Postoperative complications were the most common etiologic factor associated with the production of filtering blebs. Site of suture placement, incision site into the anterior chamber, use of enzymatic zonulolysis, or operative complications could not be correlated either with development, size, or location of blebs. Indications for operative bleb closure include foreign body sensation, tearing, persistent leakage of aqueous, interference with contact lens wear, and macular edema. The technique for repairing the unintentional filtering bleb has proven safe and effective.