Purpose: To describe a ciliary body tumor that was detected in a rabbit eye. Methods: For a specific experiment, the rabbit underwent trabeculectomy with mitomycin. The eye was evaluated by electron microscopy 5 weeks following surgery. Results: A ciliary body tumor was discovered in close relation to pigmented epithelial cells. The tumor cells were large with a small amount of pigment and contained prominent vesicles. Conclusions: The development of a ciliary body adenoma may be caused by the application of mitomycin. Whether the demonstrated tumor was benign or malignant could not be determined. While it could not be proven that the tumor developed related to the use of mitomycin, this possibility may be important for surgeons using this substance.