New modifications of lo-[[3-(diethylamino) propyl] amino]-6-methyl-5H-pyrido [3', 4': 4, 5] pyrrolo [2, 3-g] isoquinoline (lb) and 1-[[3-(diethylamino) propyl] amino]-9-methoxy-5, 1l- dimethyl-6H-pyrido [4, 3-b] carbazole (4b), which display important antitumor properties, were performed either on the side chain or on the intercalating heterocycle. Side chains were introduced by direct substitution of the corresponding chloro derivatives and 6-N- ...