Prosopographical dataset on patriciate families in Leiden during the period 1250-1420. The dataset comprises family names and data on administrative functions, ownership of land, houses and interest, family connections, suretyship etc. The dataset was originally created for a research project that resulted in F.J.W. van Kan's dissertation, 'Sleutels tot de macht: de ontwikkeling van het Leidse patriciaat tot 1420', (Leiden University 1988). The dataset was published on diskettes as an appendix to this dissertation. The dataset has been extended since 1988 and for that reason can no longer be seen as a separate part of the publication of 1988.