Based on various statistic and documentary sources, the present paper follows the evolution of the United Romanias population in the interwar period in a general European context, identifying bots population was, in the interwar period, one of the most dynamic in Europe, one of the essential features of its demographical evolution being the vital capacity, its birth rates surpassing other countries. This fact enabled Romania s natural population increase to remain significant, although in the interwar period infant and general mortality had high rates.