Department of Chemistry, University of Roorkee, Roorkee Manuscript received 14 June 1974; revised 23 September 1974; accepted 23 September 1974 The binding of Cu++ and Cd-H to soybean protein has been investigated \(p\)H-metrically. Interaction of these ions takes place with the carboxyl as well as the imidazole group of the protein molecule. The values of log K for metal carboxyl binding are found to be 2.03 and 1.85 for Cu++ and Cd++ respectively. These values favour comparably with the log K values of the first association constants of the interaction between corresponding metal and acetate group. The log K values for metal-imidazole binding are found to be 2.34 and 2.08 for Cu++ and Cd++ respectively.