A versatile synthesis of π-stacked polyfluorenes is described. These polyfluorenes retain their cofacial conformations both in solution and in the solid state as was judged by NMR spectroscopy and X-ray crystallography. The experimental electron-detachment energies of F1-F4 showed linear correlations with the quantity 1/n, where n is the number of fluorene moieties. These correlations allowed the estimation of the vertical ionization potential (IP) of 7.10 eV and the oxidation potential (Eox) of 0.97 V versus SCE for the multiply stacked polyfluorene donor with an infinite number of fluorene moieties. These observations with π-stacked polyfluorenes may prove to be highly relevant to the electron-transport phenomenon observed in DNA through π-stacked bases. Copyright © 2003 American Chemical Society.