The optimum conditions for the pulse-polarographic determination of tin, lead and molybdenum were investigated. The determination of these elements by means of a single polarogram was achieved. In ethylenediaminetetraacetic acid-sodium acetate solution at pH 3.5 there were three separate peaks and at pH 5.0 the peak for lead disappeared. Total tin in shipyard waters was determined at pH 5. The same method was also applied to the determination of tin in canned food.