This study is based on the results of the blood group typing (AB0, MN, RH: D/d) of two samples from Romania and on literature data. The 40 population samples used are scattered on the today's territory of Romania. Some data refer to more or less endogamous villages or groups of villages which belong to the same marriage area, some data refer to towns with admixed populations. Samples of nine ethnic minorities have been included in the study. The results have been discussed on the basis of the historical and geographical background.