Binding of dimethindene maleate to bovine serum albumin (BSA) was studied in isotonic Sorensen's phosphate buffer of pH 7.4 at 25°C, using equilibrium dialysis technique. Dimethindene maleate was bound to BSA, and the plot was curved indicating the presence of more than .one binding site on the albumin molecule. At fixed protein concentration the percentage of bound drug to bovine serum albumin was inversely proportional to the concentration of the drug. However, the binding parameters were found to be increased as the albumin concentration increased. But, the binding parameters (binding constants as well as the number of binding sites) did not change by the change of pH. Phosphate buffer and Gomori's tris-ECI buffer have the same effect upon the binding of the drug to BSA while Walpole's acetate buffer decreases the binding of the drug to BSA. Also, it was found that chloride ions had no effect on the binding of the drug to BSA. The interaction of the drug with dextrans (40000,266000 and 500000) in isotonic Sorensen's phosphate buffer of pH 7.4 was investigated. No interaction occurred between the drug and the tested dextrans under the condition of the experiment. Also, laevosan and hetastarch showed no significant effect on the binding process.