Objective: To investigate the efficacy and safety of adjunctive mitomycin when used during a primary trabeculectomy within a series of 89 consecutive patients at 1 and 2 years postoperatively.Design: A cohort study of all patients who underwent primary trabeculectomy, performed by one of us (P.F.P.), between April 1, 1991, and December 31, 1994.Patients received topical mitomycin in conjunction with a corneal safety valve incision.A trabeculectomy was considered "successful" if it resulted in an intraocular pressure (IOP) of 21 mm Hg or lower and a 30% or greater reduction in the IOP at and after 1 year of follow-up, with or without medications and without a reoperation for an elevated IOP.Survival analysis was used to calculate success rates.Results: The 1-and 2-year success rates were 85.4% and 77.9%, respectively.The mean IOP was reduced from 26.3 to 11.3 mm Hg at 1 year (n=68) and to 11.9 mm Hg at