Ethnic structure in the Temerin municipality during the 20th century is characterized by great changes. The number of some ethnic grupations was changing in the relative short period. This had an influence on the increase and decrease in the development in the analyzed area… The great changes in the ethnic structure were caused by political factors that occurred in some periods, but also caused by other demographic elements that characterize some ethnic grupations. All these characteristics caused even the vanishing of for example, Germans from this area. This paper describes in details all causes that caused the changes in the ethnic structure in this municipality. Besides, the consequences of these changes are analyzed and all relations and problems that can appear primarily between the Serbs and the Hungarians are pointed out.