Purpose: To evaluate the safety and efficacy of single-drop instillation of mitomycin C (MMC) in pterygium surgery and to compare the results with both postoperative and intraoperative application of MMC. Methods: Eighty eyes of 72 patients with pterygium were randomised into 4 equal groups: group 1 - control - bare scleral excision (BSE); group 2 - BSE with single-drop instillation of mitomycin C (MMC) 0.02% at the end of the surgery; group 3 - BSE with postoperative MMC 0.02% drops twice a day for 5 days; and group 4 - BSE with intraoperative MMC 0.02%. Results: The recurrence of pterygium was observed in 14 (70%), 4 (20%), 4 (20%) and 3 (15%) eyes of group 1, 2, 3, and 4 respectively. The recurrence rate after BSE with single drop MMC regime (group 2) was significantly lower than group 1 recurrence ( P = 0.001) and was statistically comparable to that of group 3 and 4. Scleral defects in the bare area occurred in 4 (20%), 16 (80%) and 16 (80%) eyes of group 2, 3, and 4 respectively. The incidence of scleral defects was significantly lower in group 2 compared to group 3 (P=0.0001) and group 4 (P=0.0001). Compared to group 1 and 2, a significant delay in wound epithelialisation occurred in group 3 ( P=0.003) and 4 ( P=0.004). An ischaemic area in the bare sclera developed in 8 (40%) and 6 (30%) eyes of group 3 and 4 respectively, while ischaemic area did not develop in group 1 and 2. Conclusion: Single-drop instillation of 0.02% mitomycin C following pterygium excision appears both safe and efficacious.