The application of internal electrolysis for the deposition of ruthenium-106 and iodine-125 on silver was examined. These investigations were aimed at the preparation of sealed radiation sources for brachytherapy. The current and voltage of a cell built of silver cathode and aluminium anode, immersed in electrolytes containing different concentrations of ruthenium were determined. The same parameters were measured for the cell consisting of silver anode and platinum cathode as a function of the concentrations of NaI and NaOH in the electrolyte. The changes of current and voltage of the cells as a function of duration of electrolysis were investigated. The influence of white light observed during the deposition of iodine indicates that photolysis of silver iodine formed on the anode affects the cell parameters. From the results obtained it follows that electrolysis performed without application of external electric tension is a simple and convenient method for fixing considerable amounts of both ruthenium-106 and iodine-125 on silver.