The number of 3'- and 4'-substituted 1-phenyl-6H-pyrido[4,3-b]carbazole derivatives have been synthesized and tested biologically. Eleven of the newly obtained compounds were subjected to the preliminary cytostatic screening for their activity against L1210 (murine leukemia), A498 (human kidney cancer), A549 (human lung cancer) and HT29 (human colon cancer) cell lines. Eight of tested derivatives exhibited significant biological activities, which only weakly depended on side chain length and position of the substituent.