Some derivatives of 9-aminoacridine (1) were synthesized, and their frameshift mutagenicity and DNA binding affinity were studied. The introduction of a methyl group into the acridine ring of 1 reduced the mutagenic activity and the intercalative DNA binding affinity, while the introduction of chlorine increased them. Halogenated derivatives of 1 showed higher toxicity against Salmonella typhimurium TA1537.