Flow cytometric analysis of DNA ploidy and S-phase fraction was performed on the primary melanomas and the first metastases from 55 melanoma patients with regional lymph node metastases or in transit metastases. The frequency of aneuploidy was significantly higher in metastases than in the primary tumour (p= 0.009), suggesting a higher growth potential in melanoma metastases than in the primary tumours. In 18 patients with reliable S-phase determinations from both primary tumour and metastasis there was no significant difference in mean S-phase fraction between primary melanomas and metastases. Skin metastases localized in dermis and subcutis had a significantly (p=0.012) higher mean S-phase fraction than lymph node metastases.