Cisplatin is one of the most effective drugs in the treatment of ovarian cancer. However, its therapeutic potential is limited by intrinsic or acquired resistance. Several molecular mechanisms of cisplatin resistance have been described including increased repair of DNA adducts, increased tolerance to DNAdamage, elevated intracellular levels of glutathione or metallothioneines, increased efflux and decreased cellular uptake of platinum. The most frequently observed feature in cisplatin-resistant cell lines is reduced accumulation of the drug [1]. The exact mechanisms involved have not been completely identified yet. Although some findings suggest that passive diffusion across the membrane is a major mechanism of cisplatin uptake, other studies indicate that various energy-dependent cellular proteins, which utilize ATP hydrolysis as energy source, may be involved in intracellular trafficking of cisplatin [1]. Extracellular ATP is known to enhance cellular membrane permeability, which may lead to increased cellular accumulation of anticancer drugs due to enhanced passive diffusion. Therefore, extracellular ATP may be used to sensitize ovarian carcinoma cells [2]. However, the exposure to ATP does not increase the accumulation of cisplatin in A2780 and A2780cis cells [3]. One possible explanation is a simultaneous increase in cisplatin efflux by activating ATP-dependent efflux transporters (e.g., ATP7A, ATP7B and MRP2). Therefore, treatment of cancer cells with ATP may increase both cellular uptake and efflux of cisplatin at the same time resulting in unchanged net drug accumulation. To further assess the role of ATP in cisplatin uptake and efflux, we investigated the accumulation of cisplatin under ATP-depleting conditions. ATP depletion can be achieved by using inhibitors of oxidative phosphorylation or mitochondrial electron transport chain (ETC) complex I – IV inhibitors. The latter are known to induce the production of reactive oxygen species leading to apoptosis [4]. For that reason, we chose an inhibitor of the oxidative phosphorylation, oligomycin, which depletes intracellular ATP levels by specific inhibition of the F0F1 ATP synthase.