Affinity of 9-aminoacridine, 3-amino-1-methyl-5H-pyrido[4, 3-b__-]indole, quinacrine, 2-aminofluorene and 2-acetylaminofluorene to copper phthalocyanine trisulfonate in sodium phosphate buffer at pH 7.4 was studied. Use of copper phthalocyanine trisulfonate covalently bound to cellulose has allowed the study to be done quantitatively; the known aggregation of copper phthalocyanine sulfonates in water, which would have made the analysis impossible, is considered to be absent in this system. The results show that these five compounds form one-to-one complexes with the copper phthalocyanine trisulfonate on the cellulose.