The use of different methods to improve the solubilization of membrane proteins have increased the number of proteins visualized in two-dimensional (2D) gels and have allowed great advances in proteomic studies, in the recent years. In this study we compare the solubilization of erythrocyte membrane proteins induced by three zwitterionic detergents: CHAPS, ASB-14 and ASB-16, using 2D electrophoresis. Aliquots of 60 mg proteins were added to the solution used in the first dimensional step (isoelectric focusing) containing CHAPS, ASB-14 or ASB-16 plus denaturant agents. The second dimension was run in SDS-PAGE and the spots were visualized by silver stain. We have found that 65mM CHAPS (4%) is the minimum concentration required for the best resolution of membrane proteins in 2D electrophoresis. The use of 65 mM ASB-14 (2,8%) or ASB-16 (3%) did not induce any increase in the number of solubilized proteins, in comparison to 65mM CHAPS. Nevertheless, different spots were detected when we used the amidosulfobetaine detergents, including high MW proteins. We conclude that the use of ASB-14 and ASB-16 can offer advantages for 2D resolution of erythrocyte membrane proteins. Besides the solubilization elicited by CHAPS is concentration-dependent up to 10 times its CMC. New experiments are being conducted with ASB-14 and ASB-16, at concentrations lower than 65 mM, since no concentration-dependent solubilization was found to these detergents. The effect of ASB association with CHAPS is also under investigation. Supported by: FAPESP