Purpose: Needling revision is an accepted method of management of poorly functioning trabeculectomy blebs, The authors present the outcome of the analogous needling revision of poorly functioning filtering blebs over glaucoma drainage device (GDD) reservoirs, Methods: Review of 20 patients (21 eyes) who underwent needling to the bleb overlying the GDD reservoir, with or without adjunctive 5-fluorouracil injection, Results: in the nine eyes (43%) that were considered successes (defined as intraocular pressure [IOP] less than or equal to 21 mmHg and decrease in IOP greater than or equal to 20% with no additional medication or glaucoma surgery), the mean IOP fell from 28.3 +/- 6.4 mmHg to 13.9 +/- 2.7 mmHg al last follow-up, after a mean of 1.7 needlings (range, 1-3 needlings) with mean follow-up of 14.6 months (range, 3-35 months). Needling success was associated with larger GDD surface area (mean, 267 +/- 95 mm(2) vs, 179 +/- 79 mm(2) in eyes needled unsuccessfully, P = 0,04) and use of Baerveldt implants (six of eight eyes needled successfully). Minor complications were few. Endophthalmitis developed in one patient (5% of all eyes) after needling, Conclusions: Needling revision can be useful in the management of poorly functioning GDD blebs, although the risk for severe complications exists.