Protein chromatography is a very complex process based on a combination of thermodynamic, kinetic and mass transport phenomena. By virtue of their complicated and delicate surface structures, the behaviour of proteins on various chromatographic media is not easy to predict. Together with the fact that the majority of the chromatographic media for proteins available today are not very well characterized with regard to their detailed chemical and physical surface structures, protein chromatography still has to be regarded as a predominantly empirical science. I.e. the optimization of separation conditions can only be performed by experiments in the laboratory. The scaling-up is then accomplished primarily by increasing the column diameter. This has been shown work well for column diameters up to at least 1,400 mm. The paper will also deal with the characteristics of the most important protein separation media, silica based, polystyrene based and agarose based, and with how to best optimize the conditions for column productivity, both for adsorption types of chromatography and for gel filtration.