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).