The clinical and histopathologic features of four cases of primary iris stromal cysts are reported. Though the histologic characteristics of iris stromal cysts have been well described by previous authors, their exact embryologic origin is not clear. Also, because of the relatively uncommon nature of these lesions, the most appropriate management is not well defined. In our series, routine histopathologic studies were supplemented with immunohistochemical stains for cytokeratins and S100 proteins, results of which suggested an origin from surface ectoderm. All of our patients required surgical management, although spontaneous involution of a temporary nature was observed in one case, and recurrences following incomplete removal were common.