This study examines the synthesis and cytostatic activity of new 5,6‐dimethyl‐1‐substituted‐6H‐pyrido[4,3‐b]carbazolederivatives. Their structures were confirmed by 1H‐NMR and elemental analysis. Seven of the new compounds were tested by the SRB method in vitro against human lung cancer (A549) and human kidney cancer (A498) cell lines. Biological tests indicated remarkable cytostatic effects of four