The constant-current electrolysis technique was utilized to determine the oxidation state of gold in iodide media. The products from the electrolysis of gold metal in KI with 0.1 M berate were analyzed by means of electrogravimetry for gold and spectrophotometry for I-2. At low current density, the gold species formed during the electrolysis process was Au(I) in KI with 0.1 M berate. Voltammetric measurements for the solution resulting from electrochemical dissolution of gold in 1 M KI + 0.1 M K2B4O7 on a glassy carbon rotating disk electrode enable us to measure the diffusion coefficient of Au(II) in the same medium, which was found to be 6.81 x 10(-6) cm(2) s(-1). The equilibrium of the chemical reaction between gold and iodine in the medium of 1 M KI + 0.1 M K2B4O7 was also studied. The experimental results confirmed that the complex formed between Au(I) and iodide is AuI2-. The stability constant for AuI2- was determined by direct analysis of equilibrated solutions and was found to be beta(2) = (AuI2-)/(Au+)(I-)(2) = 3.42 x 10(18) M(-2).