The objective of the Historical Population Database of Transylvania (HPDT) project is to build the first historical database of Transylvania’s population, covering the period 1850-1914. This will be carried out according to the most up-to-date methodological principles proposed in the field and will be fully compatible with the latest versions of the Intermediate Data Structure (IDS), allowing its connection to existing similar databases in Europe and North America. The project aims to cover 5-10% of the population of Transylvania during the above mentioned period (ca 5.4 milion births) thus providing over 350.000 IDS compatible entries.