This study sought to determine whether NaCl altered the plasma membrane proteins in alfalfa exhibiting differential NaCl concentrations, and whether caso4 modified the responses. Two alfalfa cultivars, Centurion and Condor, were grown in 0.5 strength Hoagland solution in a greenhouse. The cultivars were exposed to 0, 88, and 132 mM of NaCl alone and mixed with caso4 .H20 at 7 and 14 Mm caso4 for 3, 9, and 60 days. In experiment 1, roots were dried to determine their Na, Ca, K, and Mg concentration. The results were similar to previous reports in which CaS04 alleviated the salt stress by increasing K and Mg levels and reducing Na. In experiment 2, after proteins of the plasma membrane were isolated and their purity was determined by vanadate, ATPase activity showed a significant increase in the presence of calcium. In addition, total plasma membrane protein was analyzed by sodium dodecylsulfate-polyacrylamide gel electrophoresis. Salt treatments induced both quantitative and qualitative changes in proteins. These changes were affected by the length of exposure to treatment solution or the ability of the plants to adapt to the salt stress.