The purpose of this study was to determine whether topical mitomycin C could be used to prolong the patency of a myringotomy site in the absence of a ventilation tube. Mitomycin C is an antineoplastic agent used to maintain a patent trabeculectomy site in patients with glaucoma. The KTP laser was used to create bilateral myringotomies 0. 4 mm in diameter in 28 chicks (Gallus domesticus). Mitomycin C was applied to the right myringotomy site, and sterile water, used as a control, was applied to the left myringotomy site. The animals were divided into 2 groups with group A treated with freshly prepared mitomycin C and group B treated with 2-week-old mitomycin C. The patency rates of the experimental ears of groups A and B were 80% and 70%, respectively, 15 days after surgery and 33% and 7.7%, respectively, at 30 days. All myringotomy sites in the control ears were healed within 5 days. Using a logistic regression model for repeated measures, we determined the odds ratio between the experimental and control myringotomies of the combined groups to be 149.1 (P = 0.0001). We conclude that mitomycin C had a significant effect in prolonging the patency of myringotomies in chick tympanic membranes.