• Light microscopy and transmission electron microscopy were used to study an unusual case of retrocorneal proliferation of smooth muscle from an area of iridocorneal synechia in a rejected corneal graft. This membrane was composed of cells with many characteristics of smoothmuscle cells, especially the typical shape, production of a single-layered basal lamina on all sides, and massive intracytoplasmic accumulation of filaments of the typical size.