9-Methoxy-N2-methylellipticinium acetate (MMEA) was preferentially cytotoxic to human brain tumor cell lines in the in vitro primary screen of the U.S. National Cancer Institute. In the present study, the average intracellular accumulation of radioactivity derived from [14C]MMEA concentrations that were selectively cytotoxic to sensitive brain tumor cell lines was nearly 4-fold greater than in human tumor cell lines derived from the lung, kidney, ovary and colon. The extent of peak cellular accumulation of [14C]MMEA-derived radioactivity, achieved after 10-15 hr of drug exposure, was correlated positively with relative MMEA cytotoxicity in brain tumor cell lines (r2 = 0.963). A similar correlation (r2 = 0.967) was observed in selected non-brain tumor cell lines but required substantially higher (18-fold) concentrations of MMEA. [14C]MMEA radioactivity accumulation by a selected glioblastoma cell line occurred via an energy-requiring system that was predominantly sodium and pH independent.