DNA is considered as one of the main targets for anticancer drug design. The planar structure of acridines confers to the molecules the ability to bind DNA by intercalation and therefore to interfere with metabolic processes. A large number of natural alkaloids and synthetic acridine derivatives have been tested as anticancer agents. So far, a few molecules have entered clinical trials and have been approved for chemotherapy. The mechanisms of action are not fully understood. Cytotoxicity may be related to potent enzyme inhibition. Topoisomerase and telomerase activities may be strongly affected by acridines. The affinity of acridines for DNA has also been used to design new active compounds in which a DNA modifying group is tethered to the acridine nucleus. Acridine derivatives display other pharmacological properties such as antibacterial and antimalarial activities. They are also tested for Alzheimers disease.