The crystal and molecular structure of CxTHt9N304. H20, an ant|tumor agent, has been determined using X-ray diffraction. The space group is orthorhombic, P2~ 2 ~ 21. The cell dimensions, measured on a diffractometer, are a = 7.984 (1), b = 13.495 (3), c = 16.200 (3) A, and Z = 4. The structure was solved by direct methods and refined by anisotropic least squares to an R index of 0.050. The 1,4-diazepine ring has a boat conformation while the five-membered pyrrole ring is a flattened envelope. The stereochemistry at C(12) and C (13) is trans. There are one intramolecular and five intermolecular hydrogen bonds. One interesting feature is the involvement of the methoxy O atom in hydrogen bonding. A Kendrewmodels study indicates that the anthramycin molecule is most probably covalently bound at C(11) to DNA through N(2) of guanine in the wide groove and also O(1) of the anthramycin molecule may be involved in hydrogen bonding to sugar O atoms.