Naphthalimides, a class of compounds which bind to DNA by intercalation, have shown high anti-cancer activity against a variety of murine and more notably human cancer cell lines. Azonafide derivatives are also potential antitumor agents which are structurally related to the naphthalimides. Derivatives of azonafide have shown enhanced activity against various cancer models, especially leukemias, breast cancer and melanoma. Naphthalimides in general and amonafide in particular, are most probably the agents which have been involved in the greatest number of clinical trials without ever acceding to the market because of dose-limiting toxicity. This statement also reflects the immense interest that oncologists have paid to this class of compounds with respect to their anti-cancer potential. While the first generation of naphthalimides were mainly topoisomerse II poisons, some new compounds display novel mechanism of action. In contrast to the most widely used topo II poisons, including etoposide, adriamycin and their analogues, which often induce multi-drug resistance, several naphthalimide-related compounds have been reported not to be affected by this phenomenon. Multi-disciplinary approaches including medicinal chemistry, early toxicology and DMPK, in vivo activity assessment in diverse preclinical models and in-depth mechanism of action deciphering, along with the lessons learnt from previous and currently ongoing clinical trials, have resulted in the generation of a number of novel promising naphthalimide derivatives. It is thus reasonable to expect that members of this class of compounds will reach the oncology market in the near future.