Intercalators are the most important group of compounds that interact reversibly with the DNA double helix. Some of them are valuable drugs currently used for the treatment of ovarian and breast cancers and acute leukemias, while many others are in different phases of clinical trials. Intercalating agents share common structural features such as the presence of planar polyaromatic systems which bind by insertion between DNA base-pairs, with a marked preference for 5-pyrimidine-purine-3 steps. The chromophores are linked to basic chains that might also play an important role in the affinity and selectivity shown by these compounds. Bisintercalators have two potential intercalating ring systems connected by linkers which can vary in length and rigidity. Nowadays it is well accepted that the antitumor activity of intercalators is closely related to the ability of these compounds to stabilize the DNA-intercalator-topoisomerase II ternary complex. In this work we have carried out a revision of small organic molecules that bind to the DNA molecule via intercalation, and exert their antitumor activity through a proven topoisomerase II inhibition. We have tried to give a general overview of the most recent results in this area, paying special attention to compounds that are currently under clinical trials. Among those are naphthalimides, a group of compounds that has been developed in our laboratory since the 70s.