The sources that can be employed to examine demographic aspects of the Jewish population and family in 18th-century Poland -Lithuania are sparse and mostly fiscal in origin. Since this source material has been preserved only for some periods and regions, few generalizations can be made. First, the authors have referred to the most comprehensive census that was carried out in 1791 by household in Cracow province (województwo krakowskie). It does not allow for detailed family reconstitution, however. Although extended/multiple family households might have been fairly common, the twogenerational conjugal family unit seems to have prevailed, and no more than four nuclear families lived in one house. In addition, the age at first marriage was influenced only to a limited extent by the traditional practice of early marriage. D