Most iris tumors behave benignly, reflecting their small size and the high proportion of nevi and spindle A melanomas. Of 1,043 reported iris melanomas, 31 metastasized (3%). Metastasis from a spindle A melanoma is not known to occur despite documented growth and local recurrence after excision. If known spindle A melanomas are excluded from all reported spindle cell tumors of the iris, the rate of metastasis for spindle cell tumors is 2.6%. Mixed-cell melanomas have a metastasis rate of 10.5% and epithelioid melanomas a rate of 6.9%. The interval between the histologic diagnosis and death from metastases ranged from three months to 12 years, with an average of 6.5 years. Five- and ten-year mortality rates for different cell types cannot be ascertained. Iris angiography may be useful in defining the limits of tumor involvement but is of uncertain value in differentiating benignancy from malignancy. Of the 31 cases with metastases, 21 included information on the type of surgical procedure used to obtain the histologic diagnosis. In 13 of the 21 cases (62%), the tumors were initially involved with either incomplete excision or inadvertent transection before enucleation.