Circular Dichroism (CD) spectroscopy is an important technique for measuring the structure of protein biopharmaceutical products, which are increasingly important to the pharmaceutical industry. Its application tends to be rather different to pure research, in that it is more important to compare spectra of different samples or batches of material. However, this requires that spectra are obtained that are comparable, and that there exist objective methods for comparing spectra. We review the issues involved in obtaining good quality spectra, including instrument calibration, reference materials, cell pathlength, protein concentration and instrument maintenance, and the progress that is being made in these areas. We also discuss the available approaches for the objective comparison of CD spectra.