Cover: Two intercalated and two end-stacked 9-amino-N-[2-(4-morpholinyl)ethyl]-4-acridinecarboxamide ligands (yellow, space-filling atoms) bound to d(CGTACG)2 (stick model in CPK colours). Important hydrogen-bonded water molecules are shown in red (space-filling). For further details see the paper by Adams et al. in this issue [Nucleic Acids Res. (2002) 30, 719-725].