The use of gemcitabine in combination with chemotherapeutic agents, including cisplatin, pemetrexed and taxanes, is characterized by the enhancement of their anticancer activity. The analysis of the underlying pharmacodynamics has revealed that modulation of nucleotide pools, drug metabolism, and cellular DNA repair capability are the most common factors to explain the additive to synergistic interaction between gemcitabine and anticancer agents in several human cancers in vitro and in vivo.