Protein A from Staphylococcus aureus has a very high affinity for the Fc regions of IgG molecules. Immoblisation of protein A on beads creates an affinity resin which can be used to purify IgG fractions from crude serum, ascites fluid or cell cuture media. IgGBind resin is made by coupling purified protein A to agarose beads. The ratio of protein A to resin is greater than 4mg protein per ml resin. The binding capacity of the resin for rabbit IgG is greater than 20mg/ml.