The title compounds were synthesized in 9-10 steps in order to compare their cytotoxic properties to that for 1-(3-dimethylaminopropyl)-amino-4,5-dimethyl- 8-hydroxy-5H-pyrido[4,3-b]indole. Whereas the latter is a potent cytotoxic agent, displaying significant antitumour activity, the corresponding 9-propyl (and 7,9-dimethyl) derivatives were found to be > 10-fold less cytotoxic.