The tumor growth paradox refers to the observation that partially treated tumors might grow bigger than they were before treatment. The cancer stem cell hypothesis provides a model that can explain this behavior. Cancer stem cells are believed to be the organizing centers of a solid tumor. They are immortal and they populate the tumor mass through asymmetric division to produce differentiated cancer cells. If these differentiated cancer cells are killed (through treatment, for example), then space and resources become available for the stem cells to duplicate and, as a result, produce a larger tumor. I present a mathematical model which clearly supports this effect.