AIMS: To study the efficacy of laser suture lysis in the promotion of filtration and bleb formation during the early postoperative period after trabeculectomy. METHODS: This was a prospective study of 20 eyes from 20 patients undergoing trabeculectomy. Patients were entered into the study if, after a trial period of ocular massage, the intraocular pressure (IOP) was greater than 21 mm Hg 48 hours after surgery. Other criteria for inclusion were a deep quiet anterior chamber, no bleb formation, and a patent internal ostium on gonioscopy. Suture lysis was performed using a frequency doubled neodymium YAG (532 nm) laser and a Hoskins lens. The IOP was measured within 5 minutes of lysis and gentle ocular massage was employed if there was no spontaneous bleb formation. A further suture was lysed if at this stage there was still no bleb associated with a high IOP. RESULTS: Suture lysis was successful in all cases in the early postoperative period. The mean IOP before lysis was 33.8 (SD 8.9) mm Hg and the IOP immediately after lysis was 13.2 (7.9) mm Hg. Eighteen (90%) patients had successfully controlled IOP (mean 14.1 (3.6) mm Hg) without medication after a mean follow up of 6 months. CONCLUSION: Laser suture lysis is a safe and effective method of promoting filtration following trabeculectomy. It can avoid surgical manipulation of the scleral flap with its associated risks of bleb failure and thereby contributes to a successful operative outcome.