The interactions of H+ and Cu(II) ions with poly(adenylic acid) (polyA) are investigated using different factor analysis techniques. From the changes in the ultraviolet and circular dichroism absorption spectra obtained in the course of spectroscopic acid-base titrations of poly(adenylic acid) solutions containing different amounts of Cu(II) ion, the unitary spectra, the concentrations, and the stabilities of the macromolecular species detected are estimated. Four spectroscopically different species are detected for poly(adenylic acid) in the pH interval 1.5-6.8. Three of them are different conformations of the protonated form of polyA, and the other is the unprotonated form of polyA. One new species is detected in the presence of Cu(II) ion.