1. By using affinity chromatography and chromatofocusing analysis at least two major glutathione transferases, named GST II and GST III can be isolated from Gammarus italicus. 2. GST II has an isoelectric point at pH 5.0 and is composed of two subunits with an apparent molecular mass of 28 KDa. 3. GST III which has an isoelectric point at pH 4.6 was found to be an heterodimer of 27 KDa and 28 KDa. 4. The 28 KDa subunit cross-reacted in immunoblotting analysis with antisera raised against pi class GST, whereas none of the antisera raised against alpha, mu and pi class GSTs cross-reacted with the 27 KDa subunit.