Curcumin is the yellow pigment of turmeric, a natural product with diverse biological activities [1]. The previous studies over the last 20 years have confirmed its potent antitumorigenic activity in the initiation and promotion phases in two stage mouse tumor models [2]. The ability of curcumin to alter the redox status of transformed cells [3] and its desirable safety profile prompted us to investigate whether reactive oxygen species (ROS)-induced by curcumin can also alter their radiation sensitivity. Curcumin is the yellow pigment of turmeric, a natural product with diverse biological activities [1]. The previous studies over the last 20 years have confirmed its potent antitumorigenic activity in the initiation and promotion phases in two stage mouse tumor models. [2]. The ability of curcumin to alter the redox status of transformed cells [3] and its desirable safety profile prompted us to investigate whether reactive oxygen species (ROS) -induced by curcumin can also alter their radiation sensitivity.