In this work we tried to estimate the role of mitochondria in the ability of cells of two: melanotic and amelanotic transplantable melanoma lines to undergo spontaneous and camptothecin-induced apoptosis. We measured mitochondrial transmembrane potential (DeltaPsi) changes during culture without (spontaneous apoptosis) and with camptothecin (induced apoptosis) by using JC-1 staining and flow cytometry analysis. Cytochrome c release and PARP cleavage as the biological effects of DeltaPsim changes belonging to the phenomena observed during apoptosis were estimated by Western blotting. The results of our investigations showed in both transplantable melanoma cells the features indicating apoptosis: DeltaPsi changes, cytochrome c release and PARP cleavage, but the degree of observed changes depended on the phenotype of melanoma cells examined. After camptothecin treatment the changes were more pronounced in the amelanotic melanoma cells- the more aggressive line.