Objective: To observe clinically, in rabbits, the side effects of topical injection of subconjunctival cyclophosphamide, studying its role as an antifibrotic drug. Methods: Prospective study in 20 albino rabbits of New Zealand race. All rabbits were treated with cyclophosphamide, 10mg/ml in a volume of 0.3 ml, in the left eye through subconjunctival injection. They were evaluated for 1, 7, 30, and 60 days after the procedure. All the animals were examined for the detection of ocular reactions such as necrosis, hyperemia, chemosis, secretion, opacity, and iritis. Other side effects as changes in the behavior, in the feed, and the water consumption were also evaluated. Results: It was observed that from the 20 rabbits studied, three rabbits (15%) showed side effects only at the 24 hours analysis. One rabbit (5%) presented hyperemia, one rabbit (5%) had hyperemia associated with iritis, and one rabbit (5%) presented hyperemia associated with secretion. These reactions were not observed at 1, 7, 30, and 60 days. Conclusion: Cyclophosphamide subconjunctival injection induces minor side effects on the conjunctiva of rabbits such as hyperemia, associated with iritis and secretion.