The iris pigment epithelial cells of 10 human eyes were cultivated in vitro. RESULTS The iris pigment epithelial cells obtained directly by scraping were easier to grow and to be passaged than those obtained by enzyme digestion. Under the inverted light microscope, primary cells appeared multigonal and arranged in monolayer, there were abundant pigment granules in the cytoplasm, and the nuclei each of which contained 1 or 2 nuclei were relatively transparent. Pigment granules diminished in succeeding generations. Under the transmission electron microscope, pigment granules were rich in the cytoplasm and there were plenty of microvilli at the cell membrane. There were maculae occludentes and desmosomes present in the intercellular space. The cultivated cells showed positive reaction of keratin antigen in an immunohistochemical assay. The characteristics mentioned above are consistent with the criteria of iris pigment epithelial cells.