An apparatus is described for paper electrophoresis according to the moist-chamber principle. A simple method for quantitative evaluation of the different electrophoretic fractions is presented together with the limits for the normal variation of the different serum fractions. The influence of the composition of the buffer on the separation of the proteins is stressed. Addition of small amounts of calcium ions results in a separation of the β-fraction into two distinct fractions, β1 and β2Ca. The mobility of β-lipoproteins is decreased in the presence of calcium. The phenomenon was confirmed with the aid of moving-boundary electrophoresis. The refractive contribution of the lipids in the β-lipoproteins in moving-boundary electrophoresis is shown. The mobility of the main β-component containing carbohydrate and of the transferrin is not changed by calciumion.