The typical complications related to nonpenetrating surgery are the rupture of the trabeculodescemetic membrane; postoperative ocular hypertension, which requires a laser goniopuncture; fibrosis of the filtering bleb, which is best cured by local antimetabolite application; or the development of a polycystic bleb, which is efficiently resolved by needling. While small perforation of the trabeculodescemetic membrane can be handled using simple countermeasures, large breaks ultimately result in converting the surgery into a penetrating procedure akin to trabeculectomy. Other classical complications can arise that comprise shallow anterior chamber, positive Seidel, hyphema, severe inflammation, choroidal detachment, or prolonged hypotony with associated maculopathy. They can occur in other types of filtering surgery as they are not specific to the nonpenetrating procedure and they differ only in prevalence.