A series of phenanthrene-based tricyclic carboxamides has been synthesized as angular analogues of the clinical acridine carboxamide DACA, and their DNA binding, in vitro cytotoxicities and in vivo antitumour activities have been investigated. The compounds fall into two broad topological classes, where the carboxamide side chain is appended either to one of the terminal rings or to the central ring. In general, compounds of the first class showed stronger DNA binding than those of the second, and were the more potent in vitro cytotoxins. However, they were considerably less effective than DACA, both as DNA binders and cytotoxins. A 1,10-phenanthrolinecarboxamide derivative showed significant in vivo activity. As a class, these fused angular tricyclic carboxamides do not show sufficiently interesting activity to warrant further studies.