Ionic perylenebis(dicarboximide)s 1-5 were synthesized. The aggregation and liquid-crystalline properties of these compounds in aqueous solutions were investigated. In the concentration range of similar to 5 x 10(-7)-5 x 10(-4) M, the structures of the ammonium side chains and counterions did not have a significant effect on the electronic transition properties and H-aggregate formation of these compounds. However, the liquid-crystalline phase properties varied with the structure of the side chains and the counterions. Ionic perylenebis(dicarboximide)s 1, 3, and 5 with chloride ions formed nematic (N) phases from the isotropic (I) phase, while 2 and 4 with p-methylbenzenesulfonate ions formed chromonic ribbons from the I phase. Studies by polarized light microscopy and H-2 NMR spectroscopy indicated that the N phase of 5 (with gem dimethyl groups) formed at higher concentrations than those observed for 1 and 3 at the same temperature. Furthermore, the N phase of 5 was less ordered compared to those of 1 and 3 at a similar concentration and temperature, presumably due to the bulkiness of the side chains of 5 that hindered the stacking and pi-interactions of the aromatic rings.