Mitomycin C (MMC) was used as a perioperative adjunct during trabeculectomy for 51 consecutive cases of complicated glaucoma. The concentration applied was 0.5 mg/ml, and the sponge positioned upon the intact sclera was left in place for 3-5 min. At a follow-up of 6 months, information on 49 eyes was obtained. Following treatment with antiglaucomatous medication, the average intraocular pressure decreased from 31.5 to 13.1 mmHg. The number of different medications required was 0.25 after 6 months as compared with 2.6 before surgery. In 16 of the 49 eyes (33%), the intraocular pressure was below 10 mmHg at follow-up. Complications included severe prolonged hypotony (n = 9), conjunctival dehiscence (n = 4), and scarring (n = 1). Vision was reduced in 5 cases by more than 2 Snellen lines. We consider MMC to be a substance that can be used in trabeculectomies where early scarring of the conjunctiva is anticipated.