In a retrospective study flow cytometry was performed in 82 paraffin-embedded clinical stage I cutaneous melanomas. A significant correlation of ploidy to melanoma thickness was found. Using a log rank test ploidy was found significant for prognosis. However, using the Cox's proportional hazard test the influence of ploidy vanished and melanoma thickness or Clark level of invasion together with sex and location were the factors most important for prognosis.