There is much interest in using the far-UV CD spectra of proteins to compare their solution conformations but care must be taken to ensure that only true structural differences are being compared. Apparent differences in CD spectra can be caused, for example, by differences in protein concentration or cell path-length, because the magnitude of an absorption (A) or CD (ΔA) signal is proportional to both. Normalization of spectra to compensate for such effects is generally required and is often achieved using the 280nm absorption peak, whose accurate determination requires a second, independent measurement and assumes accurate knowledge of the extinction coefficient. In this poster, two ways of normalizing and comparing CD spectra without prior knowledge of concentration or path-length are described.