Kullerud’s method of formation-temperature determination has been applied to the polymetallic sulphide deposits of Sadon in Northern Caucasus, U.S.S.R. The sulphide ore occurs at three places, separated by a few kilometers from each other. They are Sadon, Zgid and Holst. Mineralogical assemblage is sphalerite, galena, pyrite and pyrrhotite. It is found that sphalerites from the above three places were formed mainly within a temperature range of 120–500° C. The temperature data are represented in the form of histograms. The occurrence of more than one maximum in each histogram may indicate ore deposition in more than one stage. From the histograms, it is concluded that in Sadon, ore deposition took place in three stages: in Zgid, in only one stage and in Holst, in two stages. These conclusions are in agreement with those arrived at by others by mineragraphic studies.