Intraocular malignant melanoma size is a significant prognostic indicator. No accurate volume determining technique has been generally utilized. Plastic models and selected geometric formulae were used to demonstrate a technique for volume calculation of intraocular malignant melanomas. The accuracy of geometric analysis is shown to be superior to previous "size" calculations. We believe this increased accuracy would be useful in following patients for tumor growth utilizing A and B scan ultrasonography as well as in quantifying tumor volumes in the histopathology laboratory.