PURPOSE: To examine the safety of mitomycin C (MMC) use in pediatric glaucoma surgery. DESIGN: Retrospective interventional case series. PARTICIPANTS: One hundred eighty pediatric glaucoma patients younger than 7 years of age (254 eyes) who underwent glaucoma surgery and were followed for at least 1 year participated. INTERVENTIONS: Surgeries consisted of trabeculectomy or combined trabeculotomy-trabeculectomy with adjunctive use of MMC. MAIN OUTCOME MEASURES: Control of intraocular pressure (IOP) and occurrence of complications were measured. An IOP below 21 mmHg without any additional medical or surgical treatment was considered a success. RESULTS: Primary congenital glaucoma was present in 98% of the patients. Sixty percent had a trabeculectomy, and 40% had a trabeculotomy-trabeculectomy. The combined surgery was performed mostly in infants up to 1 year of age. Complications were cystic bleb (19), bleb leak (4), retinal detachment (3), flat anterior chamber (3), cataract (2), and endophthalmitis (1). Children younger than 2 years of age had fewer complications but higher failure rates. The combined procedure in infants up to 2 years of age was moderately more successful (57%) than trabeculectomy alone (39%). Minimal complications seen in this group were more likely related to young age than to the type of surgery. Complications increased with time after surgery, with most occurring 2 years or more after surgery. CONCLUSIONS: Success of MMC-augmented glaucoma filtering surgery increased with age, as did the complication rate. Serious complications were uncommon in the authors' group of pediatric patients up to now. However, complications related to bleb thinning increased with time after surgery, and additional problems can be anticipated with longer follow-up.