In several tumors of different organ sites, the amount of DNA in a cell (ploidy) is associated with malignancy. We performed DNA quantitation in 21 choroidal melanomas and compared flow cytometry with image analysis in 11 of these melanomas. We modified our preparation technique to overcome problems with pigment and control cell populations in the image analysis group. Fifteen tumors were diploid and two tumors were tetraploid. Four tumors were unprocessable by flow cytometry, but two of these tumors were diploid by image analysis. Image analysis also detected tetraploidy in two tumors that were diploid by flow cytometry. During image analysis, cells were classified according to the Callendar classification and histograms were plotted for each cell type. All spindle A cells were diploid and most tetraploid peaks were formed by epithelioid cells. The use of image analysis on small samples of choroidal melanomas may be of value both in confirmation of diagnosis and prognosis of these lesions, and perhaps therapeutically, for example, in the monitoring of radiation treatment.