This study examined malignant melanoma of the iris in Denmark over a 25-year period on the basis of the files of the Eye Pathology Institute. From 1961 to 1985 a total of 80 cases were found (41 males, 39 females; median age 53 years, range 8-83). This means an average of 3.2 cases/year with an average population of 4.9 million. In contrast to malignant melanoma of the choroid, an increase was observed. The reason is not known, although exposure to actinic rays may be a factor. More than a third of cases were close to the pupil, a little less than a third invaded the chamber angle/ciliary body. Ten cases were ring melanomas. Half of the tumours were spindle-celled, a quarter mixed and a few epithelioid or naevoid in cell morphology. Iridectomy was performed in 28 cases, primary enucleation in 27 and secondary enucleation in ten. Iridocyclectomy was performed in 15 cases. All patients could be traced. At the date of follow-up (Dec. 1, 1991) eight had died with metastases; four of these were patients with ring melanoma and four with tumours invading the ciliary body. After iridocyclectomy, only one metastatic death was recorded--a case of incomplete resection. The grave prognosis of a ring melanoma is highlighted.