Results of the studies on antitumor activity of 20 acridines and related compounds (19 of them were new) in Sa-180-bearing mice are presented. Only several of these compounds i.e. C-258, C-829, C-874, and C-899(21) appeared to inhibit the Sa-180 growth; the activity of the two other compounds (C-783(21) and C-755(21)) requires confirmation in further experiments. The remaining 14 compounds were inactive. Some other general effects exerted by the compounds tested in Sa-180-bearing mice and some aspects of the structure-activity relationship are discussed.