Compounds which are sulfurated distamycin derivatives of formula (I) wherein n is 2, 3 or 4; A is a bond, a C1-C4 alkylene or C2-C4 alkenylene group; R1 and R2, which are the same or different, are selected from hydrogen, C1-C4 alkyl optionally substituted by one or more fluorine atoms, and C1-C4 alkoxy; X is a halogen atom; B is selected from formulas (a), (b), (c), (d), (e), (f), (g), (h), (i), (j) and (k); wherein R3, R4, R5, R6, R7, R8, R9 and R10, which are the same or different, are selected from hydrogen or C1-C4 alkyl; R11 is hydrogen, C1-C4 alkyl or hydroxy, and m is 0, 1 or 2; or pharmaceutically acceptable salts thereof; are useful as antitumor agents.