The results of primary trabeculectomy with and without mitomycin C (MMC) were evaluated in young glaucoma patients. The patients, 15-40 years of age, were divided into two main groups and two subgroups. In group IA, primary Cairns type trabeculectomy was performed in 24 eyes of 24 patients with juvenile glaucoma; in group IB, trabeculectomy + MMC 0.4 mg/ml in 3 min was done in 20 eyes of 20 patients with juvenile glaucoma; in group IIA, primary trabeculectomy was performed in 20 eyes of 20 patients with developmental glaucoma, and in group IIB, trabeculectomy + MMC 0.4 mg/ml in 3 min was performed in 16 eyes of 16 patients with developmental glaucoma. The success rate of the surgery was 75% in group IA, 90% in group IB, 50% in group IIA, and 75% in group IIB. There was no statistically significant difference among the groups in terms of success rates of trabeculectomies (p > 0.05).