Intracellular accumulation of adriamycin (ADR) has been reported to be influenced by cell membrane potential. We first evaluated intracellular accumulation of ADR and 3,3'-(di-n-hexyl)-2,2'-oxacarbocyanine iodide (NK-2280), an indicator of cell membrane potential, and found a good correlation between ADR and NK-2280 intracellular accumulation in several cell lines. This suggests that ADR accumulation may be influenced by cell membrane potential or the mechanisms of NK-2280 accumulation may be similar to those of ADR accumulation. Next, we observed the influence of the NA+/H+ exchanger and Cl-/HCO3- exchanger on the intracellular accumulation of ADR and NK-2280, and found that ADR accumulation decreased with increasing concentrations of 3,5-diamino-6-chloro-N-(diaminomethylene)pyrazinecarboxamide (amiloride), an inhibitor of the Na+/H+ exchanger, and 4,4'-diisothiocyanato-stilbene-2,2'-disulfonic acid (DIDS), an inhibitor of the Cl-/HCO3- exchanger, however, NK-2280 accumulation was increased by amiloride, and decreased by DIDS. The increased accumulation of NK-2280 induced by amiloride may be due to the increased cell membrane potential caused by the inhibition of H+ ion efflux and NA+ ion influx due to the inhibition of the Na+/H+ exchanger. The decreased accumulation of NK-2280 may be also due to the decreased cell membrane potential caused by the inhibition of Cl- ion efflux due to the inhibition of the Cl-/HCO3- exchanger by DIDS. However, the decreased rate caused by DIDS was greater than the increased rate caused by amiloride. Therefore, it is suggested that the decreased accumulation of NK-2280 by DIDS may be influenced by other factors apart from cell membrane potential. These results suggest that the Cl-/HCO3- exchanger may be related to both ADR accumulation, and NK-2280 accumulation, and that the Na+/H+ exchanger may be related to ADR accumulation, but not NK-2280. This suggests that the Cl-/HCO3- exchanger is of low selectivity.