['Overexpression of Bcl-2 is frequent in human cancers and has been associated with radioresistance. Here we investigated the potential impact of heavy ions on Bcl-2 overexpressing tumors.', 'Bcl-2 cells (Bcl-2 overexpressing HeLa cells) and Neo cells (neomycin resistant gene-expressing HeLa cells) exposed to gamma-rays or heavy ions were assessed for the clonogenic survival, apoptosis and cell cycle distribution.', 'Whereas Bcl-2 cells were more resistant to gamma-rays (0.2keV/microm) and helium ions (16.2keV/microm) than Neo cells, heavy ions (76.3-1610keV/microm) yielded similar survival regardless of Bcl-2 overexpression. Carbon ions (108keV/microm) decreased the difference in the apoptotic incidence between Bcl-2 and Neo cells, and prolonged G(2)/M arrest that occurred more extensively in Bcl-2 cells than in Neo cells.'] Do energetic heavy ions overcome tumor radioresistance caused by overexpression of Bcl-2?