Life course data for historical studies of demographic behavior come from a wide range of sources. Even when fundamental aspects of the data are the same (births, deaths, marriages, kinship, co-residence), data have been stored in idiosyncratic formats that are difficult to share and re-analyze. The Intermediate Data Structure (IDS) offers a new approach to sharing both data and the data analysis software. The IDS uses an entity-attribute-value format, which can hold almost any kind of data. Data elements are dated for longitudinal analysis, and we capture relationships among individuals and social contexts. Translating IDS data into rectangular files for statistical analysis requires additional software, and a library of IDS “data extraction” code is under construction.