Optimization of Copper ore benefication requires identification of the whole process, in which flotation is the main operation. Natural polymetallic ore in which activity of64Cu was induced served like a tracer. Subject of detailed measurements was a 14 chamber commercial flotation machine. As a result mean residence time 'for different granulometric fractions of natural copper sulphide was determined for all parts of flotation machine, as well as the efficiency of flotation.