Ocular lesions in horses, confirmed as squamous cell carcinoma, were treated topically with mitomycin C. Fourteen horses with confirmed ocular squamous cell carcinoma, three of which were affected bilaterally, were included in the study. Eight of the affected eyes were treated topically with mitomycin C alone; in the other nine eyes, the tumours were surgically removed and topical treatment with mitomycin C was then applied. The treatment protocol consisted of 0.2 ml of 0.04 per cent mitomycin C instilled into the conjunctival sac of the affected eye, every six hours, in rounds of seven days of treatment followed by seven days without treatment. This was repeated until full regression of the tumour occurred (up to four rounds of treatment with mitomycin C). Of the eight eyes treated with mitomycin C alone (without surgery), clinical resolution occurred in six cases. Of the nine eyes treated with a combination of surgery and topical mitomycin C, clinical resolution occurred in seven cases. No complications were observed.